We have released the second version of our tool. It now supports the backup and restore of the GMail labels. Every e-mail is now stored in the *.eml file, so you can open it using your standard mailing client (for example MS Outlook Express built in MS Windows). GMail labels are stored in the *.txt file, so you can change the assignment of the messages to your labels.
This release is still testing version, so you might loose your e-mails. The e-mail backup functionality should be Ok, but you have been warned. There is also the clear command, which completely deletes everything from your GMail account. Don't use this command unless you are 100% sure what you are doing!
Happy testing and thank you for feedback!