I think I've called my entire phone book
I'm on my 3rd iPhone 4. The 1st one was broken out of the box. The 2nd one had proximity sensor problems. Apple store replaced it with my 3rd phone. It has the same proximity sensing problems as the 2nd. Average 2 unintended button presses per call. So I alternately put callers on hold, hang up on them, turn on my speaker phone, or make random calls. Obviously, with this version of the iPhone, the emphasis is not on "phone." Apple says it is no longer replacing phones with PS problems; apparently too many of them to fix.