I decided to take Microsoft up on their offer and upgrade to Windows 10 for free

Except I didn't want to stay on the 32-bit version. I wanted 64-bit Windows. So I tracked down the 64-bit Windows 7 I'd had available as a student through MSDNAA and decided to switch from that. Before doing so I wanted to test what the transition from my current Windows would look like. I downloaded an image using MediaCreationTool and upgraded from it. It took a while but was done within 20 minutes. I extracted the key from the system and saved it, just in case.

I then installed 64-bit Windows 7 and ran through the same procedure — imagine my surprise when the key for 64-bit Windows 10 was identical to the key for 32-bit Windows 10. The algorithm generating it evidently doesn't care about architecture.

The following hours were spent turning off unnecessary features (disabling the sending of all kinds of data to Redmond, uninstalling/disabling unneeded components, and configuring things). I'd recommend the PowerShell script created by Disassembler — you can easily adapt it to your own needs. So far the new Windows don't strike me as revolutionary improvements in any particular way… but time, I think, will show that switching to them was a good decision.

P.S. Whoever figures out why there are both classic and "Metro" apps in the system gets a gold star!

Update – 22.8. It appears that even after "uninstalling," Metro apps remain in the system. They're merely Staged, ready for a new user. In my case, even though I'd removed them under the Administrator account, the user account still had them installed. So you need to run PowerShell under the user account and with their permissions to "uninstall" the apps.