Rated 5 out of 5 stars
I use it in a production environment, with tons of everydays mail: it is a real life savior! Despite of two annoyances it is perfect!
1. About once a week plugin starts to include a random emails to the threads - it requires just to restart TB.
2. Conversations, starting from 50 mails long - are opens very slow.
But I'm sure i will get better! :)