I have not received the OTA yet for my N7-12, but I already factory reset it in prepreparation. One theory of mine was that the install would go much smoother and quicker without it trying to optimize 200+ apps on the device to the new ART run time. I have heard that process alone takes forever and may even hang up the tablet with so many apps to get through. If I ever do get the OTA, I will immediately reset it again just to start fresh. Honestly, this Android release will probably be the N7s last, so why not start fresh and go from there.
I do wonder how many of those with poorly performing N7s after upgrading would be fixed with a reset? Of course it's a PITA, but it's either that or have a useless device. I've also seen reports that turning off Google Now fixes a lot of the performance problems.