Terrible slowdown on 8.1.
Seems to run fine on 10. Don't have windows 7 so I can't test it there.

Glad to know this wasn't just me! Thought it was really weird there was such slowdown for such an old port... hopefully this is easily fixed somehow...

Yeah, this sucks. I tried several compatibility modes and launching as admin, but still getting sluggish gameplay. All the wraparound stuff works fine.

I sent a request to Support, and while we weren't able to get it working, the newest hotfix does seem to have made a significant difference to performance.

Now I'm not sure whether this is a problem with the original emulation or not, but it seems there are some weird hiccups while playing, but the hotfix does make a big difference (but still not a smooth experience atm).

Wow, thanks man, I'm always reluctant to send support tickets for anything less than complete failure to launch or crashes.
This update made the games work perfectly for me, I'm very happy now that I can play the classic Castlevania for Halloween. :D