I personally love the Aimpoint. I own a 2 MOA COMP M3. They've got great battery life, they're really reliable. For close quarters stuff, they're great.
I've used ACOG TA31RCO's on the standard issue M16A4's in the Corps. I really like them. Some people don't like them because they're not as good as iron sight
for the known distance rifle qualification just because with iron sights, you can make a wind call and adjust for distance and then aim normally, whereas
with the RCO you have to offset aim, which isn't ideal. However, in a combat situation you probably aren't going to be making a wind call and adjusting for
distance so the bullet drop compensator in the RCO is nice. Also, the prism inside focuses the reticle off in the distance, so you don't have to worry about the target
being out of focus.
Some people knock the ACOG because of it's magnification, but with some practice, the Bindon Aiming Concept can be applied very nicely.
A buddy of mine has an EOTech that I've used (not sure on the model). It's nice, but the battery life can't compare to the Aimpoint. The EOTech also weighs a little
more and supposedly isn't as rugged, but the reticle is nice.