Nexus 7 2012 & Lollipop Performance Problems
For many owners of the original Nexus 7, the release of of Android 5, Lollipop, has been something of a nightmare. In particular, many users are finding that the performance of the tablet has worsened to the point that it is almost unable. I've found a quick fix that worked for me.
Get to the settings menu, (even that took a while with new UI), and click to disable 'Location'. Click again to enable it, but this time, uncheck the 'report to Google' check box. The table was noticeably faster after that, and also seemed not to using so much battery. YMMV, best of luck.