I came from Verizon and I live in the very populated Hampton Roads area of Virginia. AT&T coverage is not nearly as good as Verizon. More bars in more places by butt!
I'm sending feedback to Apple and AT&T. I love my iPhone but it sucks to have 1 little bar in my house now when I had full coverage with Verizon anywhere and everywhere I went.
I'm in almost the same situation. I'm in Northern Virginia, switched from Verizon which I had no problem with and am now getting 1-2 bars with my 3g iphone. Hopefully it will get better over time, but once my fiance gets hers (the benefits of getting a 16gb white) I may do some experiments and then eventually contact both apple and AT&T.