I have a Nexus 7 tablet, which I enjoy very much. It currently runs Android "KitKat" 4.4, and I have been waiting for the new version, Android 5 "Lollipop" to become available as an update. I have the 2013 version of the Nexus, but there have been more than a few posts concerning the 2012 version of the Nexus 7 not handling the Lollipop update very gracefully (see the comments after this upgrade article). If you own a 2012 Nexus 7, you may want to hold off a little to see if this gets sorted out.
It's unclear yet if these issues are present after upgrading the 2013 version, as the upgrade has not "rolled out" to all users yet. I will probably wait for a couple of weeks myself, till the smoke clears.