Rated 5 out of 5 stars

Awesome! I installed the xpi from dlech's github page (https://github.com/dlech/gmailbuttons/tree/IMAP_fetch_test) and he actually made it happen! I know it is still very early stages but he has real gmail labels working!

Maybe there will finally be a proper, unified solution to managing gmail in thunderbird using the tools available.

My dream for thunderbird and gmail:
- Only IMAP sync the all mail folder and trash folder.
- Keeps only one copy of any given email on your system.
- Use gmail X-GM-LABELS to create the inbox and sent folders by searching the All Mail folder for the proper label. Then when you archive a email out of the inbox it will delete the X-GM-LABEL for inbox.
- Use gmail X-GM-LABELS to create smart search folders for labels
- Use X-GM-THRID id's to create the conversation views. Gmail already does the work (more accurately than thunderbird conversations)

Can anyone make this happen?

This review is for a previous version of the add-on (0.4.1). 

Props to polybizman for getting into the source code.

I have good news: The folks behind Thunderbird are actually planning on making suggestions above,or something very like it, a part of the core Thunderbird product. (https://bugzilla.mozilla.org/show_bug.cgi?id=721316).