Switched to Sonic.net about 2 months ago and love it! Twice the speed (getting over 6 megabit now) of AT&T and for 1/2 the cost ($40/month vs. almost $80).
The price? $20/month. But I am not in USA.
edit: Someone should create a website that both tests your speed, but then also shares that result with the world (anonymously). I'd love to pop up a list of ISPs in a specific city and see exactly how accurate their listed speeds are before buying.
dslreports.com has speedtest results, down to zip code, though they don't include things like what service product and/or whether the service has some bandwidth cap.
Top download speeds by country: