LLVM/Clang is still under heavy development; can it be trusted for such an important task? The license is right but what about its stability? GPLv3 should never have happened; there was nothing wrong with v2 but there is a whole slew of things wrong with v3. gcc 4.4 is a major step forward in gcc's evolution but its license is a major step backward. But anyways, if LLVM/Clang were to be considered production-quality across the board, then I think it would be worth seriously considering...I seem to remember it being previously used to build the FreeBSD kernel with some success.