I've been running Win2k for about 6 or so months (maybe even over that now) and I must say it's the best operating system Microsoft ever released. Sure, it has its bugs (a lot fewer then 98) and it consumes more RAM then any other.. but it is stable! The guy before me was right about the RAM thing. To run 2k pro (the other versions are unneeded and would kill any computer) you should have 128 megs at least. I have 256 and I don't have any RAM issues with memory (at all). But 128 could run 2k and UT fine (I used to do it).
Back to your question though. No, I have not had any problems with games running Win2k. Actually I have had fewer problems with it then I had with 9x. I get higher FPS in 2k then in 98 in UT also (quite strange but I'm not complaining). The rumors of 2k having problems with games came from the beta days of 2k (I used to run the beta releases). They were stable but had a few problems running a lot of stuff. That isn't true to this day so don't worry about it. I run every game I used to including UT, Half-Life, StarCraft, Age of Empires (1 & 2).. and a few other various games. However, DOS will not have sound for games. If you have any old DOS games then you may not get sound. I found a way around this with a DOS sound emulator but it is quirky and isn't supported by Microsoft. Other then that, clear sailing.
Back to your question though. No, I have not had any problems with games running Win2k. Actually I have had fewer problems with it then I had with 9x. I get higher FPS in 2k then in 98 in UT also (quite strange but I'm not complaining). The rumors of 2k having problems with games came from the beta days of 2k (I used to run the beta releases). They were stable but had a few problems running a lot of stuff. That isn't true to this day so don't worry about it. I run every game I used to including UT, Half-Life, StarCraft, Age of Empires (1 & 2).. and a few other various games. However, DOS will not have sound for games. If you have any old DOS games then you may not get sound. I found a way around this with a DOS sound emulator but it is quirky and isn't supported by Microsoft. Other then that, clear sailing.