If you're having lag problems on your Nexus 7 after the 4.2 update...

.. do yourself a favor and wipe it. I received my Nexus 4 last Friday and I got spoiled by the super-smooth experience so I decided to do something about the lag on the N7. It is again super-smooth, thank God. There's no excuse for Google messing this up so bad, of course and now I have to re-install everything but at last - the nasty lag that made me hate my Nexus 7 is gone. Good riddance!