It's not an RMR, but I have a Deltapoint on my SBR. As far as the size and form factor goes, I'd say it was a great choice for an AR style rifle. With the proper riser there is zero dot-hunting. It lines up just the same as my T1s do.
I've only put a few mags though it, so I can't speak to its durability at this point, but as far as ergonomics and co-witnessing, it seems solid.
