If you're running 32bit at the moment, I doubt you'd see vast improvements from upgrading your OS. I think the main benefit to 64bit as far as gaming is concerned is that it gets you past the 4GB (or whatever it is) RAM barrier.
This is the major benefit from x64. As a 32 bit system, 4gb is all you get. 4gb Ram is now becoming the low end of the scale, and you're probably going to need 8-12gb soon to run games like Battlefield 3 and MW3.
To the person who posted the question, upgrade if you can to 64 bit.
___________________________________
If we're Terran, let's fly our CC's away! If we're Zerg, let's MASS QUEENS! If we're protoss, let's MASS SENTRIES! EPIC MINDGAMES!
Some Ling-Roach-All-in-Fake-Expo-10-pooling from Jerry there - Dox's bauss casting
Even the smallest donations help keep sc2sea running! All donations go towards helping our site run including our monthly server hosting fees and sc2sea sponsored community tournaments we host. Find out more here.