What do you plan to do with your AR? Are you going to train or compete with it? Are you looking to shoot long, short, or intermediate distances (or a little of everything)?
At the moment I am pondering my optic setup on my AR as well. In the end I would like to have the ability to do a little of everything, but don't want to have to buy a lot of different hardware. I already have a nice 3-9 Bushnell and would like to give it a try. That is why I am considering the Nikon M-233 mount. I am leaning heavily towards the EOTech EXPS-2 holographic sight, which can be used with the irons.
There in lies the problem because my AR doesn't come with iron sights (it arrives next week). I want the Troy folding battlesights, but they aren't cheap (around $160 for front and rear). The EOTech I want is around $500 and after plunking down a $1000 for the rifle I don't have the cash to buy them all right now. I am probably going to get the irons first and then go from there, although I would love to throw a quality optic on it day one.
The middle of the road is all of the usable surface. The extremes, right and left, are in the gutters.