I had the opportunity to install a copy of COD2 in XP, after I bought COD 2 for OSX.
I found that the MAC had a higher ping (65 to 70 opposed to 35 or 40) on the same servers, and amount of people, at roughly the same time of day.
I found my mouse to be "jerky" on the mac compared to the PC (i am using a G7 cordless logitech). I also had problems with the video not seeming to keep up - no i ddint do any tests on frame rates or anything, but i coudl feel the differecnce, especially when i hooked the box up to my 40" bravia.
I ended up buying COD4 for the PC, and not waiting for the MAC version. I would love to play it on the MAC, adn maybe COD4 will run much better than COD2 does, but until i could test it out, i would stick witht the PC version.
(keep in mind i am an old school pc user - i started on apples but gave them up after the first lucas arts x-wing game came out)
BUT I STILL LOVE MY