First of all the build quality. They are solid and heavy, and cover your whole ear, the microphone is bendy and feels like it won't pull off in your hands. The leads that connect to your soundcard however do look and feel very thin and flimsy. An accidental foot caught could potentially snap these without much effort.
The vibration effect is incredible. If you play war games like Call of Duty or Battlefield they improve the immersiveness dramatically with explosions really shaking your head! This alone makes them worth the money for gamers.
The sound quality is a little muddy and needs some tweaking with your EQ to get them to sound great. A good quality sound card really helps, if you are using on-board sound don't expect studio quality sound.
Lastly, and the reason I only award three stars, is the discomfort after prolonged periods of use. I often play games for 3-4 hours at a time, and these make my right ear really hurt after an hour. Not my left for some reason, maybe I have odd ears, but I'm not the only one this has happened to.
So, if you have small ears, want head rattling explosions and are not too concerned about awesome sound quality, I highly recommend these. Audiophiles, look elsewhere.