The problem is that a lot of new buyers think that somehow a bare bones combat rifle is somehow inadequate. Iron sights and no rail accessories have done a pretty good job of putting down the enemy for a long time. At least get used to the weapon in its original state before you start adding toys.

That being said, a good Aimpoint or EoTech is a nice addition faster target aquisition. Any combat advantage you can gain from the addition of toys is good......but in the grande scheme of things the better combat advantages are using cover and concealment properly, using movement, and firing quickly and accurately.