The discussion of the trade-offs between different internal implementations of closures, continuations, and lexical scoping was enlightening.

I'd like to hear more about the specifics joys and frustrations of building this all on top of the CLR. Are there any plans to compile down into .Net assemblies?

There's another open source port called IronScheme that's pretty far along. You can find it at:

http://ironscheme.codeplex.com/

Why not port it to JVM?

If he was porting it to the JVM, one could just as easily ask "Why not .NET?" I get the impression that his choice of VM is, with respect to his project, arbitrary and not important for his goals.