Arma II worth buying and is the online any good ?

Just wondering if Arma II + Operation Arrowhead are any good. I have watched some youtube videos and it looks pretty good, but want to hear other peoples opinion who have actually played the game. Also is there online play available ?

Download the free version and check it out for yourself.

I hear it's kick ass, this free-to-play version sounds even more brilliant.

If you don't know what you're expecting, you might be disappointed-- and what you should expect is a combat sim. Some things may seem clunky, but if you're going in for a very particular experience (ie: oh **** getting shot at by enemies and hiding underneath the humvee) then it will be a very special game for you :P.