The holosun is pretty sweet. Picked one up from kaleoarms.
Drawbacks are its new, its a little large(wont fit on my pistol rack in my safe while the rmr just squeezed in), buttons are much too small, auto adjust brightness not as good as trijicon, seems the glass cracks kinda easy in a couple of reviews, and it just looks cheap, even airsoftish. Thinking about carefully painting mine to hide the chinesium.
Pros are the window is a little bigger than the proven miniature dots out there, and the reticle is surprisingly crisp and much easier to acquire than just a dot. I even dig the circle reticle with no dot option. Its hard to tell because the dots are different sizes but i think it may just be crisper than my rmr06..