Nokia 6820 / 6820i

Ok, so I have been reading a lot of different things on here about this phone not working with the AIM client that is supposed to be on the phone, etc... My question is, if I buy a 6820 that is locked to AT&T, will it work with Cingular, (I'm guessing it will because Cingular took over AT&T), will AIM on the phone work, and will bluetooth with the phone work? Any help with this would be much appreciated. I was really excited when I found this phone because I really want a phone with a qwerty keyboard, camera, and bluetooth. Was thinking about getting the moto a630 but found it was too much of a hassle getting it to work properly with 850mhz networks.