I just updated to 15002 last night. It took 2+ hours, I went to bed after a while. Had to leave the computer on all night because the Install Updates and Shutdown Option only goes 1/10th of the way through the process before shutting down. So stupid.
So this morning when I log in I have to wait another 30 minutes while it updates my profile. When I finally get in my whole profile is busted to hell and the explorer doesn't even work. I finally found a guy on reddit who posted that unplugging his extra monitor fixed the issue. I was pretty skeptical, and tried a lot of other options including reboots, new profiles, etc but when I finally tried that it all worked.
Haven't tried multiple monitor gaming but that's pretty flakey to begin with anyways.