Damn how I wish I had read your post before! I received this update last week, yes, on January 2015, and happily (and stupidly) updated Android, thinking "yes, 'til now, all updates have been improving my Nexus 7 performance and look & feel.
Wrooooooong! Lag after lag, it's becoming almost impossible to use my Nexus 7. Now it's as slow as the worst Android tablet in the market. On top of that, several apps crash, like FireFox, FireFox beta, Dolphin Browser, etc. Even Chrome and Facebook crash after some minutes of usage.
Plus, after I reboot the tablet (it even takes longer to boot than when I had KitKat) it still keeps in memory all the apps you were using, so... when the heck does the memory clean itself???
How I wish I could switch back to KitKat, but without rooting AND without losing my personal information.
I mean, I can backup my pictures and contacts but... what about the progress in my games? I would have to start over each game and get to the current levels.
Seriously, why would they release such a slow, unefficient and crappy looking operating system? Android was great as it was, no such improvements were needed. Damn! Take it back to what it was! I hate when I slice down the LEFT menu or the RIGHT menu and BOTH menus show at the screen CENTER! Why would anybody want to mix up alerts with system configuration menus???
I hate Lollipop. I doubt the next Android version is like KitKat.
I'm serously thinking of ditching my Nexus 7 and get an iPad.