Google has started pushing a newer build of Lollipop — Android 5.0.2 — to the Android Open Source Project (AOSP). It has also pulled the Android 5.0.1 factory images for the 2012 Wi-Fi Nexus 7, and replaced it with the one based on Android 5.0.2.
Many owners of the 2012 Nexus 7 reported performance issues and various bugs after updating their tablet to Android 5.0. It is very likely that Google has fixed some of these bugs in Android 5.0.2, which should help in alleviating the poor performance issues.
The OTA rollout of the update is yet to begin, but you Nexus 7 (2012) owners can always manually flash the factory image if they are tired of the various performance issues plaguing the tablet. You can find our guide on how to flash a factory image on a Nexus device here.