If it's anything like the claims of similiar services before, it will not actually speed up your downloading of video files, if that's what you're thinking.
All of the similiar services I've heard of only speed up the downloading of text webpages. Basically the server is capable of recognizing the text, compressing it, and sending it to you computer over the 56k modem. All other elements like sound, and video are usually already compressed and will not be compressed any further. So if you're surfing mostly text webpages, you'll notice that it will load faster. You'll still be waiting hours to see the movie trailer you're downloading.
I'm basing this mostly from my research of
Juno Speed Band