For those with a slow nexus 7
If, like me, your nexus 7 has slowed down considerably since owning it, and resets don't do much for you, I might have a solution.
First, the obvious, uninstall all unnecessary apps and delete unnecessary data from your device.
Then, access Developer Settings (go into about phone and tap the build number until you have access)
Choose to limit background processes to 4. This has a slight impact on multitasking, but it's really not been an issue for me so far. The last couple of apps I've used resume with no problems.
Reboot. And enjoy! By the way, I'm aware that this "fix" is a compromise. But I've noticed massive improvements in performance, with no negatives elsewhere. If you don't like it, it's easy to change back. Let me know if this works for you, and if you have any ideas for improvements!
Another little tip which could work for you; try switching to a stock wallpaper, and disabling Currents, some people report it works!