Those that have upgraded with problems, you're forgetting the difference between the operating system and device drivers. Video cards, network cards, trackpads are all made by vendors other than the OS, or even PC makers.
If the maker of the computer does not have upgraded drivers, check the I/O makers site and download them. If they're not available you're out of luck.
Microsoft had a compatibility check program that would tell you what may not work BEFORE getting the free V10 upgrade. Failing to do before installing the upgrade will take some sleuthing around on your part, hopefully the network drivers are intact and you can do that or go to another machine to research the drivers.