The new C backend has been pushed to the repository and it seems to work without a hitch. No particular effort has been directed at making it efficient (and none will since this backend is only a temporary measure). Initial testing shows it to be around 40-50 times faster than the interpreter.
Writing this backend was surprisingly easy; low-level Grin (LHC's intermediate language) can be directly pretty-printing as C code. By far the hardest part was giving up on LLVM and settling for C.
Future development will focus on grin-to-grin optimizations and a native code generator.