Importing old emails into Gmail via IMAP

So Gmail added IMAP support this month and the biggest benefit I got from the new addition was a simple way to import my pre-Gmail email. When I first got my account several years ago I looked into importing all of my old email messages into my Gmail account but found it would be tedious and fraught with problems. The biggest one being there seemed to be no way to import the emails and preserve their old header information such as who sent it, what address they sent it to, when they sent it and when I originally received it. All the import tools I found were nothing more than glorified resenders that simply emailed my old emails to my new account. But now with an IMAP link between Gmail and Apple Mail, my current email client, importing my old email is as easy as dragging and dropping them into my Gmail inbox. Unfortunately Apple Mail 3.0 is still flaky and trying to move too many emails at once causes it to crash. If I import them in about one-month batches it seems to handle it. With seven years of email to import, I'm about three-quarters of the way through the import after three nights of importing a month, waiting, moving the next month, etc. But it's going smoothly and all the original header information is preserved accurately as well as the attachments to the originals.