I had exactly the same issue. I went from having a totally stable Lumia 920 to the exact opposite after the update. The first symptom was that Bluetooth suddenly dropped and would not be enabled until I rebooted the phone. Next, the phone started randomly freezing (requiring a soft reboot). Given the stability I had for a few weeks, I uninstalled every app I installed the day the phone and the freezes seemed to stop. However, every live tile I had stopped refreshing. I went straight to a factory reset because I thought that it may be necessary to have a clean slate after the update. It's been close to a day and everything is running fine. The apps I uninstalled to stop the freezing were The Weather Channel and Yelp, so I don't think they were the problem as I did not read any reviews from other users with similar issues.
I'm a big fan of WP8 but one of the things that swayed me to move from iOS was that I read how fluid and stable WP was . While WP8 is incredibly smooth and fluid, it's proving to be extremely unstable (as compared to iOS) I can live with the fact that a few of the iOS apps I have are not available for WP8 and that the app quality on WP8 is lower than on iOS. However, I've never had an iOS device randomly freeze up on me or even crash and reboot. Also, given the lack of a unified notification system, the live tiles are a necessity rather than just being nice to look at. If I abandon WP8 it will be because it doesn't do what it's supposed to do, not because I've got unrealistic expectations about what it can to.
Also, thanks to the users for the tips on restarting live tiles that stop working.....far easier to do than a factory reset