As far as I know right now, those of us with 8.1 Preview will have to do a clean install of the release version of 8.1. We will have to reinstall all of our non Modern apps, but the Modern apps will either reinstall from the windows store, or they will be un effected by the 8.1 upgrade. When the 8.1 preview was announced, it clearly stated that the release version would require a complete re installation of regular desktop style apps.
I, for one, have found it more reliable and easier to wipe the ssd and then do a clean install of the new os. The ssd is so fast that it doesn't take a long time. I was looking at back up media at Fry's last night. 2 TB external desktop Buffalo HD for $99. I already have about 6 TB of external storage, but only $99 for 2 more TBs would be a good thing. How can you go wrong.
Finally, I depend on Paul Thurott's winsupersite.com for the latest upgrade procedures that he tests and writes about.
