Keep in mind XP deep down is the exact same as 2000. So if you want to make the move now, feel free to do so. I personally have used 2000 as my only recent gaming OS since RC1 of it in mid 1999. I have an older system around for my really old games (Aka the ancient DOS only games that barley worked back then, etc...)
(And now before I get hit by the XP people, let me explain my statement).
For all that matters, XP is the same as 2000. They both are the same kernel, and both can run new versions of Direct X. Both run the same drivers. The big difference people are finding is that the compatibility tools in XP are easier to use. But the tools from XP work fine in 2000. So if your willing to work with the compatibility tools in 2000, you can avoid upgrading to XP. (Personally I have no use for IE6 integrated, WMP 8 integrated, System Restore, Driver Rollback, More fluffy wizards , an interface I have to spend quite a bit of time reverting to normal, and the other crap I see in RC1).