I recently moved off of Gmail and now run my own personal/family E-mail server, and I have to say so far it has been pretty pain free. I probably just haven't been doing it for long enough to run into trouble yet. Bog standard Debian install, Exim4 + dovecot + SpamAssassin. TLS, SPF, DKIM, and other acronyms all set up and working. The initial setup was a few days config file tweaking (why don't these things come working and secured out of the box?), but since then no issues--knock on wood. My only complaint is the spam filtering so far is not as good as Gmail's was, but I probably just need to better configure things. Bookmarking this guide for later!