I used one once at a LAN for about 10 minutes playing Prey deathmatch. I can't say I liked it very much, but the guy who brought it liked it and was certainly competent with it. See if you can find one to try out first, as it is quite a different style from a more conventional mouse.
Amen, its amazing how little people know of the interesting joy that comes from using about 50 dollars worth of ammunition at a shooting range. Something about the smell and kick that makes it one hell of an enjoyable experience.
Couldn't have said it better myself. However, to the OP, if you are piqued by it, it wouldn't hurt to try it. You could probably always return it. I say give it shot. Who knows...maybe your kill count will go up, if even by a few. Even a few is good for something like this.
I even though I never got my hands on the actual think, from the look of it, the position of the hand seems for comfortable than regular mouse. TBH the pistol mouse fps looks ghey and uncomfortable, don't think you can get much control out of it, just a fancy look. The zalman one on the other hand is just mouse with different angle grip, despite the look, turn your hands 90 degrees and it should just feel like a regular mouse, which might give a nice refreshing feel to pc gaming without changing the actual experience much.