They're Sennheiser so they're not terrible. I'd actually go check out LinusTechTips on Youtube, he's been doing a number of gaming headset reviews of late and he's of a pretty good mind when it comes to audio quality.'
That being said, I maintain, as others do, that you'd be just as well served by a good set of stereo headphones. As said before, most, though not all, surround sound headphones rely on software to mix the audio from surround down to stereo. Your computer will actually do that for you already. All you really need is a good pair of headphones with solid imaging and good bass extension.
I do a lot of FPS gaming and I never noticed a difference in my ability to perceive directions with 'surround sound' headphones vs. standard stereo headphones. And this isn't because I can't tell, I've regularly been accused of hacking for being able to turn 180 degrees and shoot someone coming up behind me. They think I'm cheating, truth is I have very good headphones and can hear their approach. Ever played Left 4 Dead 2? Can't tell you the number of times I've turned around and shot a hunter perched high above me...