What I did was restore to factory as mentioned here, then installed iOS 8.0.2 from scratch. I did NOT restore from backup. It seams like a lot more work but you get a really clean install. My photos, music, calendar, etc I synced back.
The price you pay is you have to redo any settings, reinstall Applications. You loose your old text messages and history.
What you get is an iPad 2 that performs pretty well, and on my 32GB I have 10GB free after clearing out all that cruft! I have heard iPads get slow when storage gets tight but I can't confirm that.
One other thing, I disabled Background App Refresh completely and a few location services like...
System Services;
Location-Based iAds OFF
Share my Location OFF
Frequent Locations OFF
Diagnostics and Usage OFF
Popular Near Me OFF
I intended to sell this iPad 2 if it went bad, but its good enough I’ll keep it. Not blazingly fast, but usable. For example I can easily watch Netflix with a fast WiFi.
One last note, when you first run your applications they start slow, after things get cached it gets much better. The only application that seems to start slow all the time is Facebook, I hope they'll fix that.