I think headsets are overpriced and prone to breakage.
Just get solid music headphones with at least a 30mm or 40mm diameter drivers/speakers, and add a cheap desktop-standing mic. Window is absolutely correct! You really haven't played CS/NS if you haven't played it with bass, or in other words, good quality sound. Sometimes, those headsets have smaller drivers/speakers that just don't do the game justice.
And like Window said, it's a lot easier to find out the position/location of enemies with good quality headphones. I've been called a hacker many times in CS simply because of good headphones (claiming I was wallhacking). Although for whatever reason, I'm not as effective with sound positioning in NS. Perhaps too many ambient sounds interfering? Or my cheapie soundcard?
Other advantages? You can use your headphones for other uses, like portable music like an MD/MP3/CD player. It's kinda funny walking around in public with a headset that has a microphone sticking out of it.

Also, you only have to replace what breaks down (headphones or microphone), whereas in a headset, you must replace the whole thing if one aspect of it is damaged.
Well, there's my honest recommendation.
