The modmic sounds incredible when plugged into a soundcard. This is an example of when I had it plugged into my old Creative X-Fi Extreme Music:
http://dl.dropbox.com/u/5977077/modmic.wav
And this is an example of it plugged into my motherboard audio(my soundcard died):
http://dl.dropbox.com/u/5977077/modmic_onboard_audio.wav
There is no reason for anyone to get a $100 desktop mic for gaming/mumble because quite simply, it won't sound as good as a decent mic positioned close to your mouth(hint: modmic). The modmic is quite a fine product, it sounds fine on motherboard audio, and sounds incredible if you happen to have a dedicated sound card. Unless you want to have a big white ball sitting in your face while you play, buy the modmic. You won't regret it.