Installed the 8.1 upgrade with zero problems. It is somewhat better than 8. With any upgrade you should backup any critical files, but again I had no issues.
I have learned to like 8.1 over 7. I have made the background of both the standard desktop and the new start screen the same and can switch between them by pressing the windows key on the keyboard or by clinking the windows icon in the lower left corner. By having the backgrounds the same the tiles seem to pop out of the picture and when I click on the program I want it flips back to the desktop seamlessly. I have next to zero icons on the desktop (I'd rather look at the background picture).
I find having my most used applications on the start screen easy to use, and access to less frequently used easier with the tiled interface than the old start button. Could just be me.