I'm running the Windows 8 Upgrade Assistant right now before ordering it and downloading it. This is a four-year-old Dell machine so I do expect it to work fairly smoothly. It was also a fairly popular model as it came with a Core i7, 24 GB RAM capability and it was very inexpensive.
Looks like I have 10 compatibility issues. I need to do some software updates to fix a few of them and I need a driver update if I want BlueTooth to work - it sent me to Broadcom's page to look for an appropriate driver.
Windows Media Center isn't included so that's a purchase item from Microsoft. It's a free download for now though.
It looks like it's going to take about half an hour to upgrade a bunch of software products and look around for some Windows 8 drivers before I can purchase and download.
Update: some of the software pieces require a new version ($$$) to upgrade to a Windows 8 compatible version. I think that I can live without them. I can always use a Windows 7 PC.
I imagine that the typical user wouldn't be able to do this upgrade without help.