Windows. Running XAMPP on Win 7. Working in 5.1.3 at the moment, just because I started the project on that version. Rebuild cache takes 2 minutes 30 seconds, just timed it.
If you are working in Windows, you might need to speed up your localhost:
http://stackoverflow.com/a/14635402 There are several suggestions on that thread, the one I linked to worked for me. If you are working on a Mac, then I am clueless...