There was a trivial bug in s2layers/compile-all.pl that didn't even let you compile a theme. Guess nobody had touched that yet, eh?
Two themes are included now for the "Super Simple" layout.
The style edit page lets you choose your theme now.
Next will be creating user/theme layers. Most my time today was spent racking my brain over how I wanted the UI. That's resolved though.
mart: weren't you going to keep your core S2 layer up on the web somewhere so I can slowly feed off it?