Fix for Nexus 7 Lag Issues on 4.2 - Culprit may be Google Currents
Some users have been complaining of pretty bad lag on their Nexus 7s ever since updating to Android 4.2, and there is an unofficial fix if this problem is happening with your tablet. Apparently, some people are finding that the lag issue may be caused by Google Currents, but this can't be 100% confirmed because neither ASUS nor Google has acknowledged that there is a problem.
Some XDA users have found that disabling background syncing for Google Currents should clear up any lag issues that you're having on your Nexus 7. So, if you're having the problem, just pop open Google Currents, tap the menu button (the vertical ellipsis), go to settings, and uncheck the "Enable background sync" option. Alternatively, you can go to your device settings, and the Google account settings to disable Google Currents sync.
Let us know if you've been having problems, and if this helps.
Source: Nexus Tablets via XDA
Re: Fix for Nexus 7 Lag Issues on 4.2 - Culprit may be Google Currents
I haven't noticed anything like that with mine... hmm.. I'll have to look into that. My son mostly uses mine :)