Well, if the performance gain is enough, I certainly would. (The codebase I'm thinking of is not huge, but large enough that I think modules would make a significant compile speed difference.) I think that with the current implementation, if your header files are sane (no depending on previously included files) you can autogenerate a module map file, one module per header, and have it just work. But I'm not sure if there are any wrinkles, because in the current state all I was able to achieve was clang crashing.