Recently I went ahead and tried an upgrade to Windows 10 on one of my PC's. Not my main one. I don't trust new software on release day. Always something wrong. After installing I noticed only a few issues that I'll share.
1. Any video player I had on that system failed miserably to run any format of video. I generally use VLC, but tried Windows Media Player, and a couple other free to try just to see if it was just those particular ones... nope. Every format of video was choppy and laggy. Even the intro movies in NWN were the same way. My guess is video drivers weren't doing well with Windows 10. Almost convinced because occasionally it would just black screen while playing the sound. Strangely Youtube seemed to run fine. @_@
2. NWN on the other hand actually worked better in Windows 10 than it did in Windows 8.1. On rare occassions in W8.1 I crash to desktop when starting NWN. It's rare, and reinstalling hasn't fixed it, so I haven't considered it so much an issue that I ranted trying to find a solution. However I didn't experience it once in Windows 10, aside from that video lag it was golden.
3. The NWN Toolset on the other hand wasn't doing so well. I don't know what difference it has compared to NWN that W10 hated so much but loading modules slowed near to a halt. Areas took at least triple the time to load in W10 compared to W8.1. Even compiling scripts seemed to take twice as long.
Every computer is different so I can't say for certain others will have these issues. I've heard W10 has had issues with Nvidia cards, which is what I exclusively use, so maybe that was the major problem. Dunno.