I didn't intend to take the Win 10 upgrade to my 8.1 desktop, but my desktop developed some severe problems that looked like they could be caused by a virus, but none of the three anti-virus programs I tried could clear up the problem. Much to my surprise, even a "reset" didn't fix it! It was almost unusable, so two days before the end to free Win 10 upgrades, I took it as a last resort, as I had nothing to lose, as otherwise I was going to have to throw my CPU away and buy a new one.
Well, much to my surprise, since the upgrade to Win 10, all the problems my computer had are gone! Plus it runs faster than before. We use Classic Shell.
As a result, with one day to go on the free Win 10 upgrade, I upgraded my wife's Win 7 machine to Win 10. It runs faster and she is happy with it.
I did keep my laptop on Win 8.1 because its main usage is when camping, at which time I am tethering it to my Android phone. The difficulty of controlling when the Win 10 Home updates come, plus the fact that there are reported difficulties with getting FoxFi to work with Win 10, caused me to leave the laptop on Win 8.1.