btw you can edit the title of your thread within a small period of time if you like to In terms of loosing data it is not supposed to if you go the beaten path ....
Upgrade should not be a problem, mine went okay. But I suspect it was because my data was backed on two external drives. I'm sure if I did not have any backup and had to rely on a 100% flawless upgrade, something would have gone wrong. (Shorter answer - You do have a backup, right?)
I've never used an upgrade on mine or anyone elses rig, but in testing and VM, etc i have done it many times and am actually surprised how well it works nowadays if you abide by their guidelines and aren't using a hacked to the brim AIO wim and setup files. Even with the latter it goes quite well.
Upgrade using "Keep Programs and Settings" should work as long as you remove any programs or specialized drivers. Got a VM program that has some hardware handling stuff installed? Remove it before upgrade Got a Nvidia driver with a bunch of control software installed? Remove it Got a Virtual Network driver installed? Remove it See the trend? Anything related to hardware, remove it first before upgrade. If you do that, you should be fine.
Got a buddy who lost his bios password on Win 8 to 8.1 upgrade on an Acer notebook. Not out of the woods on that one yet. ...T