Did you know that <a href="http://lists.llvm.org/pipermail/llvm-dev/2006-August/006492.html">Apple is using LLVM</a> as a critical component of the Mac OS 10.5 OpenGL stack?  They use the LLVM optimizers and JITs for 4 architectures (x86-32/x86-64/ppc/ppc64) to accelerate software paths in the OpenGL stack.