I was wondering if any of you people have ever used the Knights Armament Company's 600 meter flip-up rear sight.

Looks like a very solid piece of work to me, but then again, what do I know?

Any of you ever used this sight, and how does it stack up next to some of the others, like ol' #40? It looks like a winner to me, but I'd like to hear your thoughts.
[img]albums.photopoint.com/j/View?u=1242673&a=9213640&p=46996486[/img]