I gotta say you've done a great job, there are some issues here and there like the fact that if you hit a wall at the right angle you can walk right trough it but I assume this is an issue you're already aware of, I've been trying this on two different configurations (A500/1200) and both worked fine, I am pretty excited about the future of this project, keep up the good work!
I've been wondering about stairs that you've previously hinted on, how much of a performance hog is something like that?