I have one on a .22 revolver, and another on a cross bow. I really like the concept, especially for fast shooting when the range isn't too far.
I've been looking a little bit for another red-dot for the gun at the top of my wish list, a AR15 M4 carbine. The selection is overwhelming. Prices from 30-40$ to more than you'd ever want to pay for a good scope. I don't think that they are all parallax free
"Dot on target, you're on target".
but that is definately a feature that I want. I suppose that this is another case of you get what you pay for.