I’ve had Mail.App up and running with the Google Apps account I use for work with POP for a very long time. Recently, I tried switching to IMAP instead, and it worked okay (not great, but just okay). It was slow and I had to turn off all the rules I had created in Mail.App for the POP mail because that was causing all kinds of havoc (moving messages around from the IMAP account to local mailboxes and so forth). But I tolerated it because it was new and interesting; a new tech toy.
Now Mail.App craps out whenever I start it up. Short of completely nixing ~/Library/Mail is there really anything I can do? It’s been a while so I honestly can’t remember if I’ve already tried deleting the account and re-adding it. I’ve been using the web interface in the mean time, and it’s certainly workable, but it’d be nice to play with IMAP again (heck, if for no more reason than just to have some decent message filtering options).
I tried using GMail with Thunderbird via IMAP and just couldn't do it. I went back to POP3.
I think it was because it was just thrashing about, trying to make sense out of the junk mail folder (which POP3 apparently ignores). But ultimately, I'm just not sure, and POP3 seems to be happy again.
Since I don't use GMail for my primary account, and my primary account works fine via IMAP in Thunderbird, I didn't worry about it too much. :)