There is a noticeable pause at 99% even when the update functions properly as Jim notes. I have had it lock up before as Mr. Robinson observed though. It isn't often, but I have encountered it. If the update takes longer than normal (waiting an hour is definitely longer than normal), a forced reboot and second (or if necessary even a third) try at the update has always worked without any problem for me.
If I am uncertain if the system is locked up or just at a pause in the process, I push the Mute button at the bottom of the screen. If I hear it "click" on or off I know that the system is still responding. If, after pushing a couple of times, I hear nothing, it is likely not responding and it's time to give it the reboot. I'll wait another few seconds and try again. If the mute button still doesn't click, then I force a reset with the power button.
