Why buy an LCD? Barring COPS and a slight weight difference, the LCD can do everything the IR3 can.
You can pick up some really nice deals on 2nd hand LCDs because the market has gone daft and assumed that now the IR3 is out the LCD is suddenly a crap marker - go figure.
Ciaran
Only the later IR3s have the optical boards, the early models use a microswitch just like the LCD. The best benefit of the new optical board (other than taunting early buyers of the IR3 like me) is that you can set the trigger pull to half the width of a human hair - they didn't specify which sort of hair, but I'm going to use pubic hair for mine.