Old School: The Boring Beige Mic
After using the Razer Megalodons and the Sennheiser PC 350s, I hooked up an old beige analog microphone to my computer and decided to give it a try instead of a dedicated headset to see if I was really dependant on a headset for my multiplayer gaming.
Single-player gaming is naturally a different story. If you primarily play single-player titles and don't need push-to-talk or any other sort of voice communication, a pair of headphones are a better investment than a gaming headset—that is, unless the computer is in your own space and you can hook up some decent speakers.
Predictably, using my desktop mic was easy enough—just plug it in and let Windows handle the audio processing. Unfortunately, because the microphone was low-end, it didn't do any noise reduction. Additionally, because it had to sit on my desk, it was farther away from my mouth than I liked, so my friends had trouble hearing me clearly while we were playing together. If I dared turn up the microphone gain too high, I would pick up feedback from my speakers, also sitting on the desk.
A high-end gaming headset isn't required for your gaming experience by any means, and it won't even make you a better gamer in the strictest sense (though many competitive gamers playing first-person shooters swear by the advantage of headphones). What a premium gaming headset does get you is a well-aimed balance between superior audio quality (and, in some cases, better positioning when someone is trying to sneak up on you) and superior voice quality in multiplayer games.
There's nothing more frustrating than teammates repeatedly asking you to speak up because they can't hear your warnings or instructions, and you don't want to be "that guy," who everyone else has to mute or turn down because their microphone is so poor.
In the end, it may not matter which headset you use for gaming, but if you spend much time listening to music, want to hear in-game sounds at peak clarity, and you want to be understood when speaking, you're likely better off dropping some cash for a premium headset. If you can compromise on audio or voice quality, more affordable headsets can get the job done just as well.