Wacom users found Windows 7 frustrating and Windows 8 even more frustrating due to numerous pen experience “enhancements” that interfered with their typical usage of the pen in creative applications.
The quick summary on Windows 10 (including the recent Anniversary Update relesed in 2016) is that the experience hasn’t gotten any worse.
If you’ve been holding out on upgrading out of fear of how it would affect your Wacom pen, don’t wait any longer.