So far I have had no compatibility issues with Win 8.1 on 2 machines with the exception of beta 1.007 where I had an issue with a section of the Reloaded map (on both machines). That issue was resolved with 1.008. Win 9 or 10, though, may be a completely different story. One piece of advice I can offer is to install with Admin privileges. I got in the habit of doing this with every program. I also set compatibility mode for Win xp sp3. I honestly don't know if that made any difference as I just did it automatically. One interesting thing I discovered was that I had a few programs that would not run in either Win 7 (with those same settings) or XP SP3 but do run in Win 8.1 with those settings.
MAME Cab PC: i7 4770@3.4Ghz (passmark 9945), 12GB RAM, Win 8.1/64, GeForce GTX645 (passmark 1898); Shiny new laptop: i7 4800MQ@2.7Ghz (passmark 8586), 16GB RAM, Win 8.1/64, GeForce GTX870M (passmark 3598); Old laptop: i5@2.3Ghz, 8GB RAM, Win 7/64, Intel 3000 graphics
