I'm currently watching the Scripting and Dynamic Languages on the CLR session from the PDC. Rodrigo (creator of Boo) is there, and it's a very interesting discussion. I still think that Boo is the best language on the CLR, mainly because I, as a user, can write what I want, and not how I want it.
Rodrigo mentioned the IReflect interface, which was new to me. Any idea what is it used for in the CLR right now, beside Type?
On adding keywords to the language: VB.Net & C# took different approaches. VB.Net just added new keywords, C# hacked them with optional keywords.
Oh, and meta programming is fun.