Call quality pretty consistent. I always always have signal, usually have 3G. There are a couple of dead spots, maybe 100 yards with no signal.
Calling customer service is a crap shoot. I've had to call them maybe 5 times this year. Of those 5 CS calls, 2 have been excellent, 2 have been mediocre, and one has been horrible. All of them, however, eventually took care of what I needed done. The horrible one was just a very unprofessional CSR, late at night, seemed obvious he didn't want to be there. Even he came through in the end.
I've had Nextel, Sprint, and T-Mo service over the years. AT&T is better than Sprint, better than the old Nextel, and at least as good as T-Mo.
Could they be better? Of course! I hope they get there!