I have been using this for a week and have problems with the camera and proximity sensor.
1. The holes at the back are definitely not big enough for camera. I have blurred black edges in mypictures !
2. My iphone4 is totally working ok with it's proximity sensor (v4.01). The proximity sensor (placed right above the speaker) is partially covered by the belkin case. So whenever I make a call, iphone4 assumes that I am holding it next to my face and dims the screen. Each time, I had to open the case and get the phone partially out to restore the display.
As it causes the iphone4 screen to dim during any call, the case is useless.