I have had no major problems. However, I didn' t like the Windows 10 start menu, so I upgraded to the latest version of StartIsBack, which makes Windows 8 or 10 act just like Windows 7 in terms of the start menu--if not even better.
Also, the upgrade went very well. It kept preferences and installs for all Microsoft products, including Sql Server and its tools, Visual Studio, and Office 2010. Most other programs also still worked, usually keeping my preferences, which is just wonderful.
Most amazing of all, my VPN still works! It's Cisco, and when I tried connecting to the VPN at work, it politely updated itself and connected as usual. I didn't even need to reconfigure anything. It's by far the easiest upgrade I've ever undergone, and so I don't recommend bothering with a clean install. It's more like an UPDATE rather than an UPGRADE, in fact. Just a very long and complicated updates from 8.1 to 10.