Rated 4 out of 5 stars
It is a perfect idea.
I tried to make it working on T-Bird 3.1.2 by updating the RDF file, still does not work.
Trustedbird Forum is communicating in French only, therefore useless to publish issues there. Haven't seen any reply to English posts.
We've fixed Thunderbird 3.1.x compatibility a few weeks ago but it's not released yet.
You can test it from our nightly builds: http://packages.trustedbird.org/nightly/latest/
BTW, you can post in English or French in Trustedbird forums or bug tracker.