Rated 4 out of 5 stars

Thanks for the update :)
Some other feature requests:
- display thread with messages shrunk by default, and ability to expand messages one by one in the Gmail-like thread display pane by clicking on the header in the Gmail-like thread display pane
- ability to open a thread in a new tab, by a button in the header of a message of the thread or an entry in the context menu. Option to either display all messages header or bodies in one pane or just the standard thread structure with one mail body at a time

This review is for a previous version of the add-on (0.1).