It performs below commercial Smalltalk speeds because we wanted to keep it simple. Ian is supercharging it. There are a couple of neat things about it. People have done Squeak ports in a couple of weeks. And also it is really nice if you are in an academic environment.
Students can experiment with the internals of a pretty mature system.
Squeak has a 1980 model image. This makes it very portable and creates synergies in academia and elsewhere. It has extensions to the initial BitBlt to do color graphics on various machines. It has a warp drive on it so you can specify a non-rectangular source which you can then distort. Here is a nice color demo that has neat effects.