One note here, if you're using Google Apps, moving should be a breeze as you can just change your MX records. However, hosting your own email could be painful.

For me it is especially great since my primary email is an alias domain on Google Apps, which means i can move my primary email off of google apps while keeping my google account working (also grandfathered into their free plan).

So switching email is just the matter of picking my own host. That could take a while, however.