Literally the best multiplayer experience out there.
Please pay no attention to the "official" gamespot review, yes this game is hard, yes it will break you if you expect to just run in like COD with your brain turned off looking for frags.
NS2 requires skill, teammwork, strategy, and coordination. It requires leadership and those who put in the time to learn it (the most fun you will ever have) will be rewarded with one of the deepest and most satisfying mutliplayer experience out there.
The two sides are unique, balanced, and overall fun to play, the game never gets tiring as there is an assortment of classes, roles and way to support your team.
On top of all of that, there is an in depth RTS element to the entire game, with a bit of practice, you can hop into a commanding role and literally command the actions of your players as you strategize and coordinate to take out your enemies.
So please, ignore the gamespot review, it is an embarrassment. This game is a must have.