I am updating my iPad, it went through the update fine and now has restarted, but it has been almost 1.5 hrs and the bar is stuck at roughly 80%, does it usually take this long? If so I'll let it sit awhile longer, I just wanted to make sure first.
Okay i repowered the iPad and now it boots up with a white screen and black apple logo and says "SLIDE TO UPDATE" and now it has the progress bar again.
Hold both the home button and the power button to turn off the device. Turn back on again and it will run through the same process, but finish it rather than getting stuck. Not sure if it will help you, but it certainly worked for me.