My wife and I both switched from AT&T over to T-Mobile and the G1 this weekend. Why? Because AT&T's customer service is piss-poor. Because AT&T's network sucked and was practically unusable after Hurricane Ike hit Houston in September 2008. Because AT&T was harassing my wife about non-payment but it turned out that AT&T had received payment, they just didn't know where it was. AT&T is getting too big for itself - maybe they need to break up again.
The G1 is an interesting device but I haven't really had a chance to play with it yet.