Looks like I am growing out of the initial disappointment with Gmail IMAP. Although the mapping of labels to folders is still uncomfortable, thanks to some useful tips floating around on the web, I have been able to configure my clients much better now.
I did not have a lot of trouble with Thunderbird to begin with. I use the nightly build on Linux, it works fine with Gmail IMAP. After mapping Trash, Drafts, Sent and Spam folders to those on [Gmail], things work great. The only flaw I see is that even after mapping Thunderbird’s Trash folder to [Gmail]/Trash, Thunderbird’s Trash folder stays put. This causes the unwelcome [Imap]/Trash label on the web interface.
Thunderbird on Ubuntu Gutsy
On the Mac, I had expressed my doubts on how Mail.app would handle multiple IMAP accounts. This was because when I configured one Gmail IMAP account, Gmail folders were created at the top level. I was worried that more than one accounts would step on each other’s folders. Thankfully, Mail.app handles multiple accounts just fine. Mapping Mail.app’s Trash, Drafts, Sent and Spam folders to Gmail’s is easy. Select [Gmail]/Trash, for example, and use Mailbox -> Use This Mailbox For -> Trash from the menu-bar. Repeat that for other special folders.
So, there are some rough edges as far as the clients’ implementation of IMAP goes, Gmail labels are rendered pretty much useless - but all the clients are in sync! Not bad at all…