I switched to Windows 10 this weekend. Flawless upgrade. Everything (including my nVidia GTX 960 graphics card that everyone said would fail in Win 10) is working great.
I wish my iOS 9 (then 9.01, and 9.02, and 9.03, and now 9.1 today) for the iPad and iPhone had gone as smoothly.
How long did you have to wait for your free upgrade? I requested back in July for my Windows 7 desktop. My laptop upgrade came through in a couple of weeks.