I don't think it's really all that critical, provided you don't use the TBB to surf the web as your usual, everyday browser. The version of Firefox ESR that the Tor project distributes as part of the bundle jumped from 10.x to 17.x -- about a year's worth of fixes, etc..Again, personally I don't think it matters too much as long as you don't use it regularly. I did see something about rolling back an update to OpenSSL libs or something or other though, which is definitely disconcerting. Usually you don't downgrade something unless there's a pretty serious hole. I'm also clueless about this "can't use any of your old profile" thing. Makes very little sense to me, but it's their project... they should know, right.