I have an Elbit Falcon is is my favorite sighting device (currently on a Daewoo K2). The intensity of the dot changes based upon the ambient light. In bright light the "dot" intensity increases, and low light it gets dimmer. The change is almost immediate. I don't know why more sighting systems do not have it.
On another note, you all may laugh at me, but I have an early Red Star AR15 copy of the Colt 3X20, and except for the markings I cannot tell a difference with the Colt. I've had it many years and it has taken a beating and keeps on going. The glass is clear and it holds zero just fine. My only issue with it is " RED STAR" printed on the top.
On my Colt SP1, I have a Marksman Elite "M-16 Marksman" - that is a nice scope.