When I switched to FreeBSD, it was because of the quality of the documentation. In Linux manpages are a patchwork from various sources, and it shows; it's not rare for a manpage to be missing, obsolete, or to document another similar tool, or to be inacurrate... Much better than in many other OSes, but still nowhere as good as in FreeBSD.

Now that I think of it, when I switched from DOS to Linux it was already because I found manpages amazing. Maybe I've just a soft spot for documentation.