Broken. Auto-sync unusable. Rated 2 out of 5 stars
There are severe performance issues. When Zindus runs, Thunderbird's CPU usage will jump to 100% and stay there for several minutes. During this time, Thunderbird will be mostly unresponsive (forget about finishing the email you were typing). Another commenter mentioned that there's a good chance that this can make corruption of your drafts folder more likely - and this seems to have happened to me as well.
For now, I've decided I can't use this plugin in its current state and have disabled it.