I wonder if they ever resolved the storage deterioration problem. "One year later, the Nexus 7 has gone from the best to worst tablet I’ve ever owned" http://androidandme.com/2013/06/opinions/one-year-later-the-...
This is a trimming issue of the internal memory.
- Root the tablet (if you haven't already).
- Install lagfix (free) from the market or crosscompile fstrim and run it on your sd card.
Your tablet / phone will be fast again.