I did mine 2 days ago with the upgrade option (got a key for $15 ,downloading windows 8 from the microsoft site.
installed ok,all installed apps /documents//everything intact absolutely fine.
Bear in mind that your windows 7 has to be fully upto date before it will install the win 8 upgrade
After this I updated to windows 8.1 via the upgrade option again
Once again windows 8 has to be fuly upto date before it will install
The problem is that the online windows 8 upgrade needs 160 (around 2 gb of updates ) before it will update to 8.1
Most of these wont install automatically in a row,you need to do them manually a dozen or so at a rime,rebooting in between each batch
This took me over a day!! which was non too impressive - I can at last play farcry 4 though with my wireless pad which didnt work on windows 7