I think Windows 10 in general is fine, but the upgrade process does a poor job. For 2 of my machines, performing an update (not full wipe/install) resulted in a

I think Windows 10 in general is fine, but the upgrade process does a poor job. For 2 of my machines, performing an update (not full wipe/install) resulted in an extremely slow system. Doing the full wipe/install corrected the problem. Unfortunately, if one is coming from 7 or 8 (using the free update), you need to do the update to register your machine before you can reinstall cleanly. I don't know why Microsoft didn't just provide a Win10 product key via the update tool if your 7/8 install was properly licensed. They could always link it back to your machine to prevent sharing the key and not using it.