Love XPS2-0. Like the other Eotechs, it's built like a tank and is heavy, but I'm more accurate with it than with the irons, and it's obviously quicker. I would wish for auto-brightness control, but you can live without that. Most people don't like it that I have mine as far back as possible, but I can still get to the buttons. The advantage is a bigger field of view the closer you are to it, plus keeping the weight to the rear as much as possible. If it wasn't for the back-up sight, I might have it all the way back. On my Colt 6721, the ARMS sight and Eotech are in absolute co-witness. The great thing about any good holographic sight is that you don't have to line up the reticle/dot with anything - wherever it appears in your field of view, that's where the shot goes. I have mine loosely zeroed at 50 yds which takes the M855 about 3" high at 100. This should be good out to 200, and I doubt I'll ever take a serious shot with this carbine beyond that. But if I did, the 65MOA circular reticle serves also as a ranging device for the longer shots.