While LLVM isn't a fork and doesn't quite fit the model of the gnumacs/xemacs, gcc/egcs, glibc/linuxlibc &c. from years gone by, I do hope the new competition in the free compiler space will spur improvement and innovation in both projects. I would almost expect not only the state of free compilers, but the health of GCC itself, to be better with a viable competitor in LLVM and clang than without.