It was pretty buggy for me (battery life mainly). Although I put it on by flashing the takju system.img and then upgrading.
I gave in and just flashed the 4.2 takju stock image, and since then I have had comparatively few problems! (edit: completely started over)
One of my biggest bugbears is the change in how the camera handles screen rotation. Before 4.2 the buttons would all rotate without interrupting the image.
Now in 4.2 the whole image freezes, you get the rotation animation, and then the image becomes live again. On the Nexus 4 this might be quite snappy but on the galaxy nexus it is a really annoying interruption.
I keep trying alternative browsers, but keep coming back to stock. In ICS the stock browser is pretty great, I do wish I could get a lastpass extension for it like you can with dolphin and firefox though.