I'm using W7 on a Dell Optiplex 755, on the wife's laptop which came with W-scat/W8.1. I recently loaded on a external harddrive Lubuntu 15.1 on hers. What a massive increase in speed, though some things Linux does not have a lot of support for such as Hulu. But then she does not use her laptop for streaming, just browsing mostly.
She is stuck on her tablet mostly, she just got a new 50 buck fire, which does almost everything a PC does. We have gone through 4 tablets over 5 years, but then they are not expensive. I personally do not like smart phones, or tablets I prefer a PC. I have no intention to upgrade to W10, I had enough problems finding W7 drivers for the Dell.