This has been mentioned a few times. The iOS 6 camera app previews photos in a 3:2 aspect ratio, however the photos are saved in a 4:3 aspect ratio. So yes, when you view your camera roll, there will be black at the top and bottom of the photo.
The camera aspect ratio is the same old 3:2. The screen is 16:9. There is no other way to fit it on the screen without cropping it or having black bars. Changing the camera to wide screen was too drastic a move for Apple.