Issues I've had with the Thunderbolt- On day one I had errors with SMS sending and google navigation functioning at all. Restart fixed the issues with SMS and clearing the cache fixed the navigation issues.
After that I noticed audio quality was poor on the camcorder, and that GPS normally took about two minutes to lock. Both issues were fixed with the OTA, and so far I have had no reboots. Signal strength also appears to be slightly better on 3G post update.
The only other issue I had was one time my entire SMS inbox and outbox deleted itself. I think something happened with a conflict of getting an SMS at the same time as a phone call and also at the same time an app was trying to happen. The phone just kinda freaked and all SMS were deleted. Issue hasn't happened since.
So far I'm fairly pleased to be honest. All issues have been either resolved, or were one time issues.