AT&T accelerator is a local proxy server, nothing more. Not a bad thing, but most folk's PC's are running pretty slow to start with, adding another service just makes it worse.
I think Earthlink is the one that has a compression system set up. It compresses the images on the server side so you actually download less data, thus the page loads a bit quicker. The downside to this method is any image downloaded (buttons, pics, etc) is lower quality, often looks much worse.
Just for clarity, lets call it what it is, DSL is broadband over phone lines, everything else is its own. Broadband over satellite is not DSL. DSL is the method used to serve internet over phone lines, there is no such beast as wireless DSL.
http://en.wikipedia.org/wiki/Digital_Subscriber_Line