There was a permanent notification that I could not get rid off. I consider that forcing an upgrade. It was the 2012 version of Nexus 7 and while not everyone

There was a permanent notification that I could not get rid off. I consider that forcing an upgrade. It was the 2012 version of Nexus 7 and while not everyone had these issues, it was a pretty common problem and I consider it a huge failure on Google's part. As far as a I know, there is no way to downgrade without rooting the phone. Some people reported that factory reset helped with the performance. I haven't used it for several months and then installed CM - not as fast as the 4.x was, but somewhat usable.