I'm using Evolution on imap now and it sucks. I'd been using mutt for many years and decided it was time to try a GUI client now that most emails are fairly graphical.

Evolution will routinely chew on my disk for over thirty seconds before starting up, for no clear reason. It pops up strange error messages about host resolution when I know the host is up just fine and quite reachable. It doesn't atomically handle email moves, so I've closed the client and later reopened it to find messages I've moved right back in their original places.