Today I helped someone who had the upgrade forced on them. They ended up with a computer that booted up and they could log in, but then almost nothing worked. The start menu wouldn't open, and most of the taskbar icons did nothing when you clicked on them. The computer also showed that it was constantly in airplane mode despite currently being connected to the wifi network.

I eventually determined that the latest drivers from Dell needed to be installed, so I was able to work around the road blocks and get it updated, but it's not something the user would have figured out.

Again, how nice of Microsoft to grace him with the latest version of Windows and turn a computer that had been running nicely for months/years into a barely usable mess.