I am on the verge of finishing my AR build and have been contemplating these also. After doing some reading I am leaning more towards the Aimpoint. Better battery life and no reported issues of faulty battery compartments. I really like the reticle of the EoTech, but that was about the only thing that I thought was better than an Aimpoint.
Some of the models that were issued to line units had faulty battery compartments that caused failures in the field during use. Enough so that they insitituted a replacement. Different model, but same mechanical design through the line made me cautious. To their credit EoTech made it right to the best of my knowledge so the issue may not be there anymore.
I have had a chance to play with it now... not at the range but in different scenarios. The trick is not actually "looking at" the hologram. But still at your target. I know... Duhh!!! But at first you want to look at the image projection.
I guess what I like most about it is how quickly you can throw up on a target or move around and hold your target.
I've go tEoTechs on AK's AR' s and a M1A SOCOM. I love those things. It took a little getting used to from regular iron sights, but after you shoot a little with it, you won't want to give it up.
I took a deer with my AR last year using an EoTech on a 16" RRA carbine model. Shot it right through the neck at about 50 yards.
Also, another benefit is that my daughter shoots right handed but is left eye dominant. With these sights, she can keep both eyes open and now can actually hit what she aims at. It has made a shooter out of her.