Lighter, smaller, sharper
The GoPro Hero3 is 25 percent lighter than the previous-generation Hero 2's camera. It's also 30 percent smaller. However, all of that reduction manifests in reduced thickness with a new depth of only 20mm. The height and width (42mm by 60mm) are unchanged to maintain compatibility with GoPro's line of BacPac add-on modules and rear doors for the clear plastic shell.
On the front panel, you'll find the new f/2.8, six-element aspherical lens that is supposed to offer twice the image sharpness and reduce the amount of barrel distortion at the extremes of its 170-degree field of view. However, the characteristic fish-eye look of the video and photos captured by the Hero3 hasn't been totally removed, as it's sort of a hallmark of the action-camera style, adding a bit of drama to scenery as it speeds by.
The Hero3 uses the same improved LCD of the Hero 2, with its monochromatic dot-matrix display. I found the screen to be easy enough to navigate using the GoPro's combination mode/power button to change modes and the shutter release to make selections. However, there is a bit of a learning curve. Expect to spend a bit of time on your first outing just looping through the menus and getting used to where the options are. I also found the LCD to be a bit difficult to read in direct sunlight.

The Hero3 (right) is the smallest GoPro camera ever, edging out the previous Hero 2 (middle) and the old-school Digital Hero 5 (left). Antuan Goodwin/CNET

The front panel is also home to two indicator lights: one red to indicate that the Hero is recording and one blue that blinks to indicate that Wi-Fi is active. There are also smaller red indicator lights on the top, back, and bottom panels that are visible from most angles.
On the back panel, you'll find the removable cover for the 1,050mAh lithium ion battery. Swappable batteries are a good idea if you plan on being out shooting all day. Next to the battery door, you'll find the proprietary BacPac connection where the accessory BacPacs, such as the LCD and Battery BacPacs, connect.
On the right side of the unit (when viewed from the front), you'll find the Wi-Fi button that activates and deactivates the wireless connectivity with the GoPro app for smartphones or the Wi-Fi remote (which is included with the Hero3 Black Edition, but not the Silver or White editions). The details of how the Wi-Fi remote works have already been detailed as part of our review of the GoPro WiFi BacPac. However, this built-in Wi-Fi functionality renders the WiFi BacPac itself obsolete for this new generation -- although you'll still need it if you have a few older Hero 2s kicking around.
On the left side, behind a removable plastic panel, you'll find the Hero3's greatly simplified bank of connections. There's a Micro-HDMI output, shrunken down from the Mini-HDMI of the previous generation, and a microSD card slot, shrunken down from a full-size SD card slot for space savings. The Hero3 doesn't come with a microSD card, but supports cards with capacities up to 64GB. Finally, there's a Mini-USB port, which makes a return appearance, that is used for charging and syncing. However, with the aid of optional adapter cables, this Mini-USB port can also double as a 3.5 mm microphone input or an analog video output. I like to see GoPro doing more with less space here, but this connection scheme pretty much locks you into only using GoPro's first-party adapters, which may not be too big a deal for some users.

The Hero3 consolidates the previous generation's inputs and outputs down to two ports and a card slot. Antuan Goodwin/CNET

On either side of the Hero3, you'll find a small pinhole microphone for audio recording alongside your video. GoPro claims that its wind reduction algorithms have been improved for this generation. Like the previous generation, the camera comes with a swappable Skeleton back panel for its clear plastic case that can be used to further improve audio quality at speeds below 100 mph at the expense of waterproofing.

Rough and tumble shell
The Hero3's clear plastic shell is as much a part of the GoPro system as the camera itself and has received an update as well to match the smaller Hero3 chassis. Now thinner than before, the Hero3's shell also offers three waterproof buttons that pass your inputs through to the power/mode select button, the shutter release, and the new Wi-Fi button.
The back panel is still removable to allow replacement, for example, with the aforementioned Skeleton door or deeper doors that accommodate the BacPac add-ons. The door also features a new two-stage lock that that requires a tab to be pushed to the side before the locking mechanism can be lifted and rotated out of place. This adds a bit of extra security, keeping the camera sealed in its case, but I never really had any issues with the old, single-stage lock, so this new, sometimes incredibly difficult-to-open lock seems a bit unnecessary. Users who often submerge their GoPro cameras might not think so.
Finally, the Hero3's new shell features a new, flat lens that is supposed to work better with the new lens' reduced distortion and offer better underwater image quality.
Like every generation of Hero shell before it, the Hero3's clear shell is completely user-serviceable with the ability to replace any component from the lens to the door to the body itself independently. It also retains compatibility with GoPro's entire catalog of mounting options.

Build quality & handling

The plastic housing, like the previous version, is robust enough to be knocked, dropped, drenched and thrown about.
There's an extra lock on the top hinge which can be fiddly with cold or gloved hands, but will guard against accidental leverage of the hinge, although we did find the hinge assembly coming off from time to time.
The mount attachment is the same as previous models so you can reuse your existing mounts without buying new ones, or take advantage of the many Third Party options out there such as the K-Edge GO BIG mounts.
The only things about the camera that have got bigger are the operational buttons for the menu and shutter activation: an improvement over the previous model, as it makes operating the camera inside and outside the housing easier.

The menu system is unchanged although, as with previous HERO cameras, you can find yourself pressing the same button over and over to cycle through the menus when you've clicked past the option you wanted to change.

Performance

The metering functions cope very well across a range of light conditions and rapidly changing light conditions.
The sensor and compression improvements, in terms of quality over the HERO2, are obvious when looking at 100% crops of identical photos with a reduction in artefacts.
There is a tiny improvement in resolution and chromatic aberration is still present, but less so than with previous models.
The white balance, which can be adjusted in nerd-friendly Kelvin, isn't always right in auto mode, returning magenta-tinged blues at times, but nothing that a little post production couldn't fix.
One marked improvement is the ability to retain details in highlights. On the previous model bright areas were easily blown out, but there's a lot more detail now.
There is a sacrifice to be made in detail in dark areas, which we found when shooting into low autumnal light. But then this camera comes from California, where they love the sun.

LCD touchscreen performance

The optional touchscreen is a great addition, if only for navigating the menus. Whilst only 5cm across the diagonal it eliminates the guess work from lining up shots, and provides an opportunity to check back footage quickly and easily.
The unit doesn't have its own power supply so it is a drain on your camera's battery. There's no setting to change the brightness and the screen isn't visible in bright sunlight.
Why they chose to use white graphics on light grey backgrounds is a puzzler, when more contrasted icons would make for easier viewing.
It can be a little slow to respond to presses in video playback.
When shooting underwater, the touch functions won't work so you'll be relying on the regular buttons for menu selection.

Compared to the competition, such as the £100 ($150) cheaper Sony HDR-AS15, which already has Wi-Fi built in for live streaming, identical frame rates at 1080p and 720p plus a stereo microphone and speaker compared to the GoPro's mono and no speaker; and the £160 ($250) cheaper Drift HD which has a built in colour screen and more buttons for menu navigation, is the GoPro worth the extra money?

• Buy GoPro HERO3 Camera Black Edition at Value Basket for £254.99

Yes.
Especially if you're a professional videographer, because of the wide range of resolutions and frame rates it offers.
And yes again, if you want a small, light camera that is capable across a wide range of environmental conditions.
If you're not that worried about weight or size and are looking for a cheaper alternative, then the Sony offers a great picture for less money and does pretty much the same job.

Depending where you want to use it, the GoPro already has a mature range of mounting accessories. They're still a little flimsy and overpriced, and difficult to attach with cold or gloved hands, but it does mean that you can attach the camera to pretty much anything that moves.
With the HERO3 the main takeaway in terms of image quality was the improved detail in highlighted areas, but when shooting into the light you can lose a lot of information in the dark areas of the image.
The menu system is still a frustration too, but the LCD touchscreen negated this annoyance and we hope the free GoPro App, which becomes compatible in December for the Black Edition, will do the same job as the touchscreen, as well as making framing of shots and shooting a more controlled affair.

In sum
The $399.99 flagship GoPro Hero3 Black Edition goes head-to-head and toe-to-toe with the top of line Contour+2, which retails for the same price. Both cameras offer great HD video quality and both cameras ship with waterproof, ruggedized plastic shells to protect your investment. Both feature built-in wireless connectivity with smartphone apps: GoPro uses Wi-Fi; Contour uses Bluetooth. The Contour+2 wins a round with its ability to record and embed GPS elevation and speed data into its videos and the fact that it ships with video editing software, while the GoPro offers neither. I've also noted on many occasions that the Contour is easier for novices to use, with its slide and record control scheme.

The GoPro Hero3 Black Edition (pictured) is the best sports camera yet, but the Silver and White editions are great value alternatives. Antuan Goodwin/CNET

However, the Hero3's smaller chassis, on-device display and controls, and superior resolutions and available frame rates make it the obvious winner in a spec battle. If you're a semi-professional or prosumer sports camera enthusiast, taking an extra day to figure out the Hero3's more complex control scheme is totally worth the greater amount of on-device flexibility of shooting modes.
However, at about four Benjamins, the Hero3 Black Edition may be too much camera for your average consumer who only occasionally hits the slopes or is only uploading to YouTube or Facebook. For those who don't need 4K video or want to hold off on buying the Wi-Fi remote, the $299.99 Silver Edition and $199.99 White Edition meet the right price points, but come into competition with the newly announced ContourRoam 2.

Source
Engadget GoPro HERO3 Reviews (Critic Reviews 8.2/10, User Reviews 8.3/10)
Techradar GoPro HERO3 Reviews (4/5)
PC Mag GoPro HERO3 Reviews (4/5)
CNET GoPro HERO3 Reviews (CNET Editor's Rating 4.5/5, Average User Rating 1.5/5)

The Good The GoPro Hero3 is smaller, lighter, and features built-in Wi-Fi connectivity. The Black Edition offers a number of ultra-high-resolution capture modes and high frame rates for standard HD resolutions; burst speeds for still photos has been greatly improved.

The Bad GoPro's control scheme has a longer learning curve than the simpler slide-n-go setup of the Contour cameras. Only 15fps on 4K video renders this selling point mostly moot for action videography.

The Bottom Line The GoPro Hero3 Silver and White editions are strong contenders in the sports camera market, but the faster, more powerful Black Edition is head and shoulders the best sports camera on the market today.

Official Website

Where to Buy 
$399.99 Official Website HERO3+ Black Edition
$448.00 New Egg GoPro HERO3: Black Edition 12MP Camera with Built in WiFi, Micro HDMI Port, Supports up to 64GB MicroSD*free shipping
$229.99 Amazon GoPro HERO3: White Edition - (197'/ 60m Waterproof Housing)*free shipping
$229.00 Amazon GoPro HERO3: Silver Edition*free shipping
$199.99 Amazon GoPro Hero3: White Edition - (131'/ 40m Waterproof Housing)*free shipping
$399.99 Amazon GoPro HERO3+: Black Edition*free shipping