I've resisted most upgrades strongly (and would never have touched Windows 8), but had to give the Windows 10 one a shot 2 months ago while trying to correct a system issue.
Overall, it's been an improvement. Boot speeds are quicker and processor usage for CAD seems a little better. Biggest surprise was wireless transfer speed more than quadrupled (might have been a driver update which wasn't available for previous version). It's taken a few hacks to fully disable some of the new bloatware, but overall better. We went ahead and did all of the machines in out office over the last month)