8.1 is just an update of windows 8. its not even a service pack. just a really big update.
and there might be problems, yeah, a lot of people have had them.
if the update fails it just reverts to previous install.
when you update, everything stays the same except for what is getting updated.
none of your data will be lost, your desktop will look the same.
Microsoft refuse to put a warning on Windows 8.1 Pro preview to tell you that if you install your new Windows 8 Pro code in the System properties where it asks you to put in your own code, and when it encourages you to do that, that causes people (like me with 20 years PC experience) around 200 hours of stinking work trying to get it all working again because it causes everything to stop working and you have to completely re-install everything from scratch; including a thousand updates, and all your programs and their updates and software files, documents, images, videos, games, passwords and the million bits and pieces that take months to remember and get back to normal.
Basically EVERYTHING you put on in the two months of having Windows 8.1 preview you have to remember and do again; but with additional work.
If only smugfaced Bill Gates could feel my frustration for just an hour for what his spiteful ignorant coders have caused thousands of people across the world.....