New games are coming out for vista
I suggest you stick to Vista for now It's not gonna take along time for Games to come out if that's what you care about
About the functionality, I think it's fine.
As far as current gaming goes XP is still the best and will be for quite a while. Even the newest unreleased DX10 games can be used with DX9 and XP with a good video card. XP still owns most of the market and game programmers can't afford to not utilize that market.
vista wont be mainstream for a while, the uptake is very slow, everyone is fine with XP, theres no need to upgrade because it isnt much of an upgrade. so, for now, xp still rules
Here I've taken old 2000 and 2001 released games and seen them run better on Vista then newer 2005 games like Metal of Honor: Allied Assault that won't even install on Vista. Even new games forth coming will take XP into account due to how long XP has been the predominant version of Windows namely far longer then 9X-ME, NT, and 2000.
Most games already out are backward compatible to 2000 or ME if not to 98. Newer games exclusive to Vista will take some time until the market is there for them. Most games coming out at this time with some exceptions will be DX10 compatible Vista ready games that still run on XP. Software companies will take the fact that XP is still the main OS into account there. Vista ready and Vista exclusive are two different things.