Neat! I've been a CS TA. However, I haven't needed a piece of software like this (to be fair, your site seems to be down so I can't understand exactly what it does right now).

One thing I'm worried about is that in the past, I would have wanted my students to use their own environment rather than web. Or the software was too complicated to give them a web version. However, I can see the use for lower level courses where the assignments are not too complicated.