I have a N7 2012 that was ruined by 5.0 and 5.0.2, very laggy and frequent freezes. None of the typical remedies would fix it. So bad, I purchased a N7 2013 and kept it on KitKat 4.4.4, refusing to take 5.0.2 update.
I recently discovered the Wugfresh Nexus Root Toolkit and decided I had nothing to lose so rolled my 2012 tablet back to 4.4.4 and now it's working great again. Once I saw how easy it was to do using this tool (I consider myself mid tech capable), I decided to go ahead and take 5.0.2 on my 2013 tablet, figuring I could roll it back to 4.4.4 if things didn't work out. Lo and behold, Lollipop is running great on my 2013 N7. Very smooth, no lags, nice animations and very stable (for the past 2 days at least).
2012 N7 only has 1GB RAM whereas 2013 has 2GB and I'm guessing this has something to do with the difficulty that the 2012 version has with Lollipop. I highly recommend using this tool if you want to downgrade to 4.4.4. Although it's got Root in the title. You're not really rooting the tablet, you're just unlocking the bootloader and flashing back to an earlier version of a factory image.