I am guessing that their offer to let people upgrade to the iPhone 4 a year earlier had a lot to do with this.
That and the fact that though AT&T reception/network is atrociously bad in high population density areas like NY and LA, it's network and reception is fantastic in most of the rest of the country.
I get 100% reception and barely any dropped calls in Montana, but when visiting my family in NY, I dropped 4 out of every 5 calls I tried to make!!!
So based on where I live now, I would say very satisfied. If I ever moved to NY however, you can add me to the list of vocal complainers.