Great military simulator for multiplayer gaming.
Arma 2 is in essence an incremental 'upgrade' on Arma. There are more weapon systems and units in Arma 2, and the graphics have been modernized to an acceptable level. Once again, if you're looking for state of the art eye candy and you're expecting Crysis or Far Cry 2 particle effects, then you will be disappointed. But then, this is a military simulator that delivers everything needed in the graphics department to provide a great experience if you're into massive sandbox milsims.
Many people complain about the extremely buggy campaign, to which I have to ask, why in hell would you want to play the campaign? It follows the exploits of a group of marines in the fictional Walt Disney US army that seem genuinely caring about the poor people of the fictional country of Chernarus, which is ridiculously unbelievable. If the campaign were to feature the true to life bomb-the-hell-out-of-anything-that-moves US military, then I'd reconsider playing the campaign. In games like Arma 2 I would expect the realism to extend to all aspects of the game. But if you must play the '80s cliche good guy American campaign, then I suggest you wait a few patch releases before attempting such an endeavour.
Arma 2 really shines in multiplayer. Build your own missions where you take on incredible odds with only a few good friends to cover your back, and see how far you make it. Or build a racing map, where you compete with your friends (as civilians) to be the first one to a gunship half a map away, after which the winner gets to hunt down the losers... The opportunities truly are endless.
In all, I'd recommend this game to anyone with a real interest in anything military, and to those with a healthy dose of patience and intelligence. This game is not well suited for children, the elderly, console gamers or people with learning disabilities.