It really depends on your needs.
One universal truth about gaming headsets that I have seen repeated time and time again...
They get abused to hell and back and tend to die sooner than you would like. I wouldn't spend a lot of money on one.
Now, what are your requirements? Do you need a headset to keep your gaming quiet for those around you? Or do you just need it so you can effectively use apps like Ventrilo or Teamspeak?
If the former, don't bother with the USB sets. Just get a comfortable stereo set with a decent mic. Plantronics and Logitech both make decent ones for less than $50.
If the latter, you can do something entirely different. I hate playing with stereo headphones. I find them uncomfortable over time and my PC has excellent sound positioning and 7.1 speakers. I would rather hear the gaming sounds from them. But, my guild also uses Ventrilo.
I just use this:
It has a decent noise cancellation mic that I can easily set so that it doesn't trigger from game sound effects or background noise. It also allows me to hear everything around me. If my ear gets sore from wearing it long term I just flip it around to the other ear.
I have my soundcard/speakers set as the default audio device under windows, so all gaming stuff goes through that. Under Ventrilo I have all chat output go to the USB audio. For me, it works extremely well.
For a stereo gaming headset, you might consider:
have used that one, and it has been pretty good and sounds suprisingly rich for the price. And you won't feel bad when you walk away from your computer, fogetting to take it off, one to many times. Or when you accidently roll your chair over the cord for the 100th time exposing the copper wire.