I dunno, most games it feels like the developers were trying to make a finished-ish product for release, ARMA series it just feels like BIA's motto is to make a great base platform game that everyone in the sim community can somewhat enjoy and can be modded and scripted very easily then just let the community make it into the game they want it to be.
Yes standard AI in arma2 is smart sometimes and dumb the rest. ARMA2 with mods like Zeus and upsom means the AI tend to be a fair bit smarter.
@ comparison: you know I almost wish there was a good contender to ARMA, codemasters is a bloody joke of a competitor. Were there a REAL competitor to ARMA it would force both products to improve or loose. right now there are lots of things that ARMA should include from the hop, things like weapon resting, and editing weapon sights are only brought into the game in mods. proper animations for weapons and the ability to select components for your rifle ( aimpoint, m203) should also be added.