I find headers with templates are always the problem. So external template instantiation and pre compiled headers can solve a lot of first time compilation slow

I find headers with templates are always the problem. So external template instantiation and pre compiled headers can solve a lot of first time compilation slowness. Pimpl is more for reducing how much you have to change headers forcing a recompile during development. It's also really handy for keeping binary compatibility with published dynamic libraries so that you don't have to recompile dependants.