I know I am in the minority, but I highly don't recommend it unless you have a Windows 8.1 installation disc. First time I tried to upgrade it (from the microsoft app store) on my Windows 8 PC, it broke my whole computer (stuck in a boot loop saying it was trying to restore the previous version of Windows) and I had to wipe it. And I can't refresh/restore my operating system because I downloaded 8.1 and the windows 8 advanced boot options don't work with 8.1.
Right now, I have it kinda working and it's very unstable for me. I'm reverting back to 7 then back to 8 but I'm not going to 8.1 because it's been a disaster for me.