I played this game, did not like it very much I kept getting shot from out of nowhere and it would be over for me in about 2 minutes (However I can play BF2 and other games like this without any problem), and they won't let you play as OPFOR which I think is dumb.
US Army: "Oh no, we can't let people play as the bad guys! That wouldn't be cool"
Yes, I know that depending on what team you are on the other team looks like badguys, personally, I think that is a bit dumb.
And yes, AA is based off of the Quake 3 Engine which came out a really long time ago in 1999, well, that's a long time for computer technology.
Personally I think that the only good things this game has going for it is the fact that it is free, and the fact that you weapon can jam, I like that.