This update gave me such a headache last night. First it took forever to download and install. Then I had to download new drivers for my motherboard. While installing one of these drivers I got my first BSOD in windows 8. When I got the BSOD it wouldn't restart so I had to manually reset my pc. When I did my mouse stopped working... (not like it wouldn't move. The pointer was missing all together.).
After a couple of resets, my keyboard stopped working as well. After I reset my pc a couple more times my keyboard at least started working again. Turns out it was the Logitech drivers for my mouse and keyboard that was causing the trouble...
I advise anyone that has a Logitech keyboard, mouse or headset to uninstall the driver before installing the update. Once the update is done you can reinstall the drivers for that device. Apparently I'm not the only one that has this issue with Logitech, but its quite possible that you might get this error with other brand's drivers that are not windows 8.1 compatible.