It has a lot to do with Boo, really, particularly in the compiler. The rest of the OS is fairly similar to what you'd see in other .NET languages (although that has a lot to do with our reflectionless runtime not supporting a lot of the cool Boo functionality yet), but in the compiler the Boo list functionality has made life incredibly easy. The internals of the compiler really look a lot like that of a Lisp implementation; the code is loaded from .NET assembles into S-expression like lists, then transformed repeatedly until it becomes machine code.

No way this could've been done so cleanly in most other .NET languages; my previous .NET compilers can attest to that.