I've had my PC for just over a year. I upgrade to windows 8 pro when it became available. Every time I need to restart it, the PC installs an update. The concerning thing is that these updates can take hours. I once installed restarted the PC at 10 am, and it was done installing around 5am the next morning. All I see for this period is:
keep your PC plugged in until this is done
installing update
what's worse is that when it turns on, I get the lock screen, I then enter my password, and I get a black screen with a mouse. I can move the mouse, but I don't get the start screen. I have to do a hard shutdown on the PC, then reboot it. Then after 3 or four times, it finally loads the start screen and everything is fine.