It's ok for a free game, I somehow doubt that everytime you flashbang someone your gun jams though...not exactly the 'authentic experience' they claim. I find you get too many people with unreal engine hacks in the game.
Absolutely amazing game. I've been playing on-and-off for about 18 months now. I love the ranking system which really makes you work hard and to be careful not to shoot at team mates. It's definitely THE most realistic FPS game on available.
Also, the guns look real and sound really loud. I had my neighbour complain about the noise once.