About the only real practical complaint I have heard about them is that since the pins are in the same vertical plane it is much more difficult to gap shoot with them. I somewhat agree with this as it would explain some of the problems I had while using mine out on the 3D range this year.

I do like the ease of use which the site offers. Not having to carry around a set of allen wrenches sure is convenient. I have only had time to play around with the Flatliner model. I am unsure if the other models allow you to mount the sight closer to the riser but this is something that I think might be offered as an option.