We just switched to the iPhone 4 last month and have been having problems with reception and data speeds ever since (though our 3s weren't all that great either). I called AT&T today to see if it was an equipment or infrastructure problem and the rep. informed me that there are currently 7 towers in a 10 mi. radius "down for service" (a friend of mine reported recently that he was told it was 12 towers). He assured me that maintenance would be completed in the next couple of days and that we should no longer have any problems. In consideration for the inconvenience we've been experiencing they credited us $100 on our bill.
The other word on the street is that a lot of these outages are occurring because AT&T is swapping out the 3G infrastructure for the 4G infrastructure, which is supposed to be fully functional by fall.
For the past week or two, we've had horrible coverage in and around our neighborhood (near OPRFHS). My phone is constantly searching in my home and it was never a problem before. It's maddening.
Do you all have the AT&T Mark the Spot app on your iPhones? You can "mark" where your loss of coverage is and it sends the report to AT&T. I've been reporting my location non-stop in hopes they notice that there's a problem with the tower. The more reports the better!