I've got a 1st gen Nexus7 .

It's stuck at the coloured circles phase of bootup.
It's been like that all through the night.

I suspect it's taken an auto upgrade of some sort, but I can't tell what.

Anyway, there is something coming out which bricks these devices - so beware.

My device is out of warranty period, so I don't know how I'm going to get it fixed.

Best of luck.


Nick

My First Gen Nexus 7 has just done similar, it seemed to do some sort of Recent update, not sure if it was apps or operating system. The got message it was optimising the Apps. It seemed to be stuck in a loop ie never got to the end of optimising the Apps.
Tried rebooting it via menu and out of desperation used recovery mode. When I plug it in to PC with USB it doesn't seem to recognise it , it did before!.  So can't currently flash any files to it, with suggested tool kit i'm still trying.