I wonder if there's been any movement on the dreadful performance of 4.2? It made me very aware that there is little to no support for Android/Nexus, and nowhere to take problems unless you know what a bug tracker is, which many will not.
Stuff like better animations for the app switcher made my own Nexus 7 feel faster after the 4.2 update. Of course, that's just a perceptual change.
Prior to 4.2, Chrome with many tabs open and Adobe Reader were my only major annoyances. Chrome seems somewhat better, though since I've cut down on tab usage and started using Firefox more I'm not sure how much it's really improved. As for Reader, I just use ezPDF for larger documents now.
It's also disappointing that some longstanding Chrome issues have not been fixed.
If the option were available to go back, I would take it.