Nokia has been showing off the camera a lot on the Lumia 920 which has given us a good look at the camera app itself. One of the nicest additions to the app is the ability to pinch to zoom while taking a photo, but it looks like one feature had to be eliminated to make room.
The photo below shows the camera app in Windows Phone 7.5. You can see a sliver of the previous photo taken to the left of the viewfinder. The photo above shows the camera app in Windows Phone 8, and instead of a photo preview there is just an arrow. The change is likely due to the gestures that can be done while taking a photo. It would be easy to accidentally swipe over to the previous photo while trying to zoom in, which would get annoying fast. Plus, now the photo can take up the entire screen. Not such a bad change after all.