I had problems a while back with any long-running downloads or streaming video on ATT DSL. Basically made some uses impossible - any large remote data that couldn't resume at arbitrary points. Went completely away when I switched to a third-party ISP - using the same ATT-owned DSL lines.
I signed up for a VPN service right at the end, and that cleared everything up for me and completely confirmed they were intentionally shaping and disrupting traffic.
