I’m currently reviewing my backup plans and decided it’s a good occasion to finally start backing up my Gmail account. Firstly, I didn’t seriously consider Desktop clients as the main backup tool, as they are hard to automate. The two main options are: OfflineIMAP and getamil. Both are available from Ubuntu’s repositories, so installation is easy with both and both have good tutorials, Matt Cutts’ getmail and EnigmaCurry’s OfflineIMAP.
OfflineIMAP claims to be faster, but I haven’t really checked it (and I’m not sure how important that is giving that it runs in the background). From what I saw configuring them is mainly a task of cut-and-paste, but getmail requires to list every label you want to backup, which I consider is a major downside. As both are able to save the mails to maildir format, it should be easy to back it up using duplicity.
Conclusion: This was a short comparison, mainly to guide me in choosing the right backup for me, you may have different opinions (which, of course, I would gladly hear). I finally chose OfflineIMAP, mainly due to the labels issue.
Note on desktop clients: It seems that every decent one can be configured to work with a local maildir, so you can use them to read the backups. As I prefer Gmail’s interface, I will only use desktop clients in case I’m offline, so read-only access from desktop client seems good enough for me.