Using GMail for quite some time now, I recently got really annoyed by the kind not quite right integration in Apple Mail. Theres always this Google Mail folder with all kind of Subfolders which should really be Mailboxes in Apple Mail, also the Sent/Draft/Trash is not really working like it should out of the Box.
I then discovered that there actually is a way to set IMAP Folders to be used as those special Mailboxes, all with a Simple click.
After doing this, and copying the messages to the right folders, GMail and Apple Mail are finally working as they should, even Junk Mail filtering is now working with the right Spam Tags in GMail.
I don’t know if this feature has been there all along but I first noticed it after upgrading to Snow Leopard.
Those are the kind of things I love about the Apple Apps, integration is really key.