Wanting To Read SICP

So, /prog/ gurus, I finally decided to try to tackle what everyone has been yelling about.

First question - what interpreter is the most widely used for scheme, and which one should I use?

colleges tend to use DrScheme
some people will drop the UI and just program in mzscheme

scheme48 is also pretty nice

lot's of people seem to be using chicken, gambit, etc ...
don't go there