Based on that, here's my experience:
Got my iPhone almost 2 weeks ago. Coming from Verizon, I was immediately skeptical of the coverage because its been pounded into my head that Cingular/AT&T is not the best service in my area, although the service map shows BEST possible coverage almost everywhere I live (Northern Delaware). So going into this, testing the service, I tried to compare everywhere Verizon was great - so far I'd say the iPhone's reception has matched about 80% of the time but I have noticed the bars issue (5 to none and back in the same spot), dropped calls, spotty reception, and echoing.
After reading these posts, I called AT&T to see if my phone had the same problem and needed an OTA update. Initially I chose to go straight to an Apple rep and although he was extremely polite, I don't think he knew what he was talking about. Being an IT person I think I explained the problem as accurately as possible and he told me to fix it, I should turn WiFi on and off. That's right, in order to fix a voice issue and spotty signal strength I should power cycle WiFi. I thought voice and data was different, he said not so. So then I asked him if there was any kind of OTA update that needs to be sent or a reassigned ID (as suggested in post #36) - he said that in the next month, there will be an update to enable MMS (cool), ringtones, and all sorts of other media options. I said this was great and all, but I'm really interested in just making the phone part work - otherwise I'd just hold on to my iPod and Verizon phone.
So finally I realize I'm not going to get through to this guy so I say thanks and hang up. 5 minutes later I call AT&T customer service and speak to a nice guy (also with southern accent). He identifies that my area should have killer coverage and that I should be having no problems. Immediately he sends the OTA update and tells me to power cycle my phone in 10 minutes, try it out, and if its not improved I might have a hardware issue. I mentioned the problem about phone confusion trying to bounce between multiple towers, he agreed that could be a problem but didn't seem to know about it previously or about reassigning a phone ID. So I will try the OTA update and see if that works.
Incidentally I mentioned to him what the Apple tech said, about powering off WiFi to fix voice issues and he was borderline dumbfounded. Without ripping apart the Apple guy, he said that voice and data have been separate for quite some time, (I know).
Hopefully this will work, I LOVE the phone, but am concerned about the network.
By the way, skip through the automated menu:
1-800-331-0500 to call AT&T
Enter your 10 digit number
Option 0, then 0 to talk to an AT&T rep (for this issue)
Option 0, then 1 to talk to an Apple rep