I'm on AT&T cable (formerly TCI here), and as much as I wish I could complain about it (I hate Cable Companies), I gotta say it's been great. The speed test on dslreports usually gives me 2.5 - 3 megabits down (128 uplink).
I think the quality of the service is going to vary, depending on which company owned the system before AT&T bought 'em out. I have a couple friends on AT&T (formerly MediaOne) in some other suburbs....the bandwidth is moderately good-to-poor, and their services (mail, news, web)disappear for days without explanation (sometimes AT&T/MediaOne doesn't even admit there's a problem).
Good luck, I hope you get a good one......
Scott