From what I've seen and read and hear, Dual Core is definitely worth getting since we all know that even hardcore gamers do a lot more than just game . . .
Also we see that Dual Core will soon have an advantage over single core in gaming (i.e. nvidia 81.xx drivers) and not to mention gives single core quite a beating in general windows usage, photo editing, multimedia and of course stuff like encoding. DCs have also been proven to be much more effective at playing H.264 encoded video which will likely become tomorrow's standard.
However, why I would want to get a dual core is simple: being able to encode video, burn a DVD and play BF2 at the same time with minimal performance decrease (due to memory bandwidth) good stuff . . .