I have two on my main computer but one runs on a VM, so I'm technically not dual booting. I use Win 8.1 Pro and Win 7 Pro on my desktop. My laptop is still running its native Win 7 Home Premium. I have a couple of VMs running different Linux distros, but I don't use them very often. Out of all of the OSs I use 8.1 is by far my favorite. I don't know if I'll bother upgrading to Win 10 to be honest (side note: it'll be a free upgrade for those with 7 and 8-8.1 for the first year of its release [this is for you Pike]).