Haven't used the Aimpoint yet, although I've used both the EOTech and the ATN Digital. Truth be told, I preferred the ATN over the EOTech.
Not to suggest that the EOTech wasn't good - I thought it was pretty freaking cool actually - but the ATN just seemed to fit me better.
I can only assume that the Aimpoint would be similar, however one thing that I liked about the ATN was that there was really no "scope".. it was just a round piece of glass that you looked through with no magnification. I DID look through an Aimpoint once and I remember thinking that I liked the ATN better.