Rated 4 out of 5 stars

Ls,

This add-on seems to work on Thunderbird 3.0.5 on Linux Mint 8.
The only thing was that it didn't register as installed.
The add-ons menu was keeping the 'restart to install threadvis' notification.

Looking at the profile i noticed that the directory in the profile of thunderbird was owned by root.
When i did a:
sudo chown -R \{A23E4120-431F-4753-AE53-5D028C42CFDC\}
And started Thunderbird again, it started up and worked.

Hope this is a pointer for you if your threadvis isn't installing.

This review is for a previous version of the add-on (2.1.682).