Yes. All NT based Windows versions have always been multi processor aware, and dual/quad core is simply multiple processors on a chip as far as the OS is concerned. As far as fully harnessing the power of such a setup, thats still mostly up to the programs themselves. The OS can multithread all the APIs below the program as much as possible to improve things, but that only goes so far.

I get a ton of use out of having dual core on my Mac, and am looking forward to my next upgrade bringing quad core as a minimum. Gaming is definitely taking advantage of multicore now, thanks to the consoles and desktop PCs both forcing the issue at the same time. It's also useful for running high quality VOIP calls while playing without either impacting either process.