I installed the official Lollipop update the day it was announced. Here's the list of bugs (issues) I have found thus far...
1) Had to factory reset the device after installing the update, it went through my battery in about 6 hours when it normally last me about a day and a half. Problem FIXED after the factory reset.
2) Cannot load Galaxy App Store, I was able to do that in all previous versions, but now they blocked it.
3) Has rebooted on me twice, randomly. That's new.
4) Device vibrates randomly, I don't know if it's a bug yet but I've noticed it vibrates and there is no notification at all, or etc.
5) Memory leak still present (but that's a Google thing), sometimes it takes a while to load all home screen apps.
6) Had difficulty pairing with my Bluetooth Car Stereo (previously paired), it took a long time and several repeats/re-starts.