My pc's, laptops, tablet and phones are all on 8.1, (which is MUCH faster and stable than Win7) except for 2 with Win10. Frankly, I like it better than 8.1, so will be upgrading all to Win10 upon formal release.
Desktop; I'm currently running 7, and still performing rock solid. I'll wait and see how 10 works in the real world.
Tablet; I got the Surface RT when it first came out to try out the tablet experence, now jonesing for a Surface Pro. When the RT dies I will get a current Windows Tablet.
Phone; If I still have my Icon when W10 mobile comes out, it's a wait and see. Otherwise, I'll likely get a W10mo phone when I replace the Icon.