I had one (bullseye reticle) and sold it.

The two main failings, compared to a Aimpoint were: reticle washout when aiming from dark into light areas and blooming when in sunlight but target is in shadow.

I found the bullseye reticle covered too much of smaller distant targets. Great for close up work.

I also liked that my astigmatism wasn't as pronounced with the M21 as it is with the Aimpoint.

H