> I am very excited in hearing that it can compile to C.

You can also compile ruby to C. Does this mean the code is in general
as
efficient as hand-coded C? No. Maybe for certain purposes.

Why would you combine Scheme and Ruby? If you like Scheme, use it.

BTW there are quite a few Scheme implementations that compile to
native
code. MzScheme (PLT), Chicken, Bigloo (which compiles also to Java),
Larency (which I have never tried) etc.

> because I hear it is fast.

Frankly, I'd suggest to actually test it and ask again later.