I was one of the lucky ones who was able to update to Windows 8.1 before the installer was pulled from the store. To be honest I just started the update and left the machine, so I am not totally sue how long it took. An educated guess would be between 30 to 45 minutes. So far the verdict is pretty positive. The performance is very good, despite me using old hardware, and curiously I lost none of my apps. The two things I enjoy the most is boot to desktop and the ability to set my wallpaper as background...