We have been using Windows 10 for over six months now on our laptops as part of the insider program. I really enjoyed watching the operating system grow, change, and become even better with every new version. We had Windows 10 insider preview installed on two Asus Ultrabooks, one that is relatively new and an older one that would not run Windows 8; it just blue screened all over the place. I was pleasantly surprised when I was able to install on both of these Ultrabooks with no issue. The older one that had so much trouble with Windows 8 has not had any problems to speak of, which speaks highly of Windows 10 backwards compatibility with older hardware.
Let me just start with our company policy. It is to never ever to upgrade with a Microsoft product. It always ends poorly with our experience. I just wanted to try the upgrade process. I tried it on my own workstation, the one I use every day that has all of my software on it. I did the upgrade process with Windows 10. After about 25 minutes I was in Windows 10, I only had to restart once for the video card drivers to install. With all of my software files, pictures, wallpaper where I had left them with Windows 8.1. I have been using it all day long with no problems whatsoever.
I foresee great things with Windows 10. I will be installing this on our high-end gaming machine next to play with DirectX 12.