is at it again, and this time Tim Gaden has tracked down a method for using Gmail with IMAP in Mail.app. It might not be pretty - it's a Perl module that needs a little bit of finagling - but it apparently works. I can't even begin to fake that I know a lick about Perl, so I'm just going to have to point you to the original post
to have at it yourself.
If any TUAW readers get this to work, feel free to post your thoughts on this most sought-after of (wholly necessary) Gmail features.