I don't notice much of a difference between Win2K3 and Win2000 (had only a short experience with XP) when looking through registry and files etc... I think the biggest leap in OS support was when it switched to the NT kernel and then to the added enhancements of XP...
Besides, its a server OS and I think a majority of the changes were in favor of customer-driven (outta installation commentary LOL) requests and improved network components of the system (or in other words, Windows XP without the extras and then some)... I doubt this will affect any games or applications considering they just build each OS off its predecessor

Everything I've installed so far has worked fine... using XP installations. I'm just making a guess that game support won't really be needed for this OS considering how closely it resembles WinXP
I just hope developers will make flexible software instead of going "OMG I DONT KNOW YOUR OS THEREFORE I WONT INSTALL"

(most of them already do tho)