I have read that 3G iphones had terrible service when they came out. A client of mine had one and always complained about it. From what I've read, the newest firmware updates have taken care of most issues.
I've been using a Bold for a couple months now in the OC area and some in LA. The early OS's seemed to cause dropped calls for me at least but the newer OS is working good so far. I have dropped calls a couple of times but I'm not entirely sure if it's a phone issue or at&t.
Sorry I can't help anymore than that but it's just been my experience so far.