I have a HD2 on AT&T since 1/4/10 - granted it's Edge but with the 1Ghz makes up for it - Edge coverage is good as well - I am in Western Michigan. Running custom ROM from XDA also works great - WM 6.5.1 with Sense 2.5. Well the 4.3 screen is great - very pleased so far.
I too have ATT as my carrier since I had my Kaiser. Out here in the Rockies I often only get Edge but can ocassionally connect with 3G on the Kaiser. I've had my HTC HD2 now since before Thanksiving, an unlocked UK model (without US 3G). I'm very satisfied with it and tho I did enjoy 3G before for the times I roamed in civilization, the question for me becomes, will I or won't I spring for an unlocked 3G model when they finally hit the US.....
We'll see.
Take Care
__________________
Bill
HTC HD2,freyberry_premium_V5_28014, 16G Micro Sandisk
USMC MSGT (ret), LMSC Mission Control (ret), Colorado