Compressing-proxies aren’t new. Tools like Rabbit and Ziproxy (happy birthday) were used a lot on dialup links a while ago. But then, as we got faster links, we forgot them.
However, then are still very effective nowadays, for mobile devices like the iPhone. Public Wifi spots are often slow. These proxies make your web browsing experience way better. Really. Try to access popular web sites with and without them, and you’ll get addicted to those proxies.