Okay, so, I hadn't heard about this, so thought I'd report my experience. I went ahead and factory restored to Win8.1 using the latest image downloaded when I logged into the support site. During the initial Win8.1 setup, I was asked if I want to upgrade to Win10. That's new, obviously. I said yes, and was told the upgrade would download in the background and offer to install when ready.
That's all good, of course.
Now, though, my machine has been waiting all day, plenty of time for the upgrade to download, and nothing. So, yeah, good intentions and all that. And now I don't want to manually upgrade in case it messes up the automated process I'm supposed to have started.
Suddenly, I'm less enamored with the whole Win10 process than I once was.