The users describe it best...
- Multiple Touch Focus/Meter regions on ICS (on supported devices with Android 4.0)
- Direct access to exposure control and zoom
- One tap access to ISO, White Balance, Scene Modes, Focus Modes, and Flash Mode Settings (based on device abilities)
- Custom mapping for hardware buttons (like volume down for focus, volume up for shutter)
- Pre-focus function
- 35mm style film roll integrated with the viewfinder display
- Star your favorite photos, which will be added to their own "Stars - Shot Control" group in the stock gallery app on most phones.
- With "Instant Upload" enabled in Google+, photos with stars will be "instant uploaded" to G+/Picasa as if they were taken with the stock camera app.
- Fix for bugs with some HTC Cameras (Desire HD, Wildfire S)
- Added "HTC Zoom Bug" option in settings. Try it if you need it
- Bug fixes for a number of device specific issues.
- Multiple touch to meter regions now supported on HTC One
- Landscape orientation for either way, flip 180 degrees if desired
Required Android O/S : 2.1+