Was wondering if anyone had this on their AR15 and how it performs?  I am looking at the 3 MOA version.  

Do you need a riser mount for this?  I see they sell a version with a picatinny mount but it seems like it might still need a riser on an AR?  

If so what riser would I want to get so I could still use my MBUS?

You'll need longer screws but the 1/4" riser from the speed bead puts it right at absolute cowitness.

Don't have one mounted on an AR15, but I have several on other guns. Very nice optics for the $$$

I use one on a 12 ga. shotgun and love it.  So small and lightweight, it's like it isn't even there.

Youll need a 0.5" ir 5/8" picatinny rail riser (using the factory thin mount), or get the dedicate AR mount part from burris.

The battery life is not long enough to keep it on all the time, so its not my choice for an HD sight, and the battery lid is thin threaded aluminum and way too easy to strip the threads.

The 3moa dot is nice, and the auto adjust brightness works well enough.  Seems a bit small and fragile for some uses, but for sporting purposes its a good sight.