Bland, derivative, and very boring, World in Conflict is worth neither your time nor your money. This game is flawed on every level: the gameplay is monotonous and unremarkable; the campaign is unrealistic and tiresome; the graphics belong in a game five years older; and the developer was too lazy to even differentiate between the two sides, resulting in each unit class being identical across the factions---Starcraft bucked the trend of identical factions back in 1998, but apparently the developers of World in Conflict never got this memo. I cannot speak to the multiplayer in this game, as I did not bother to play it, but I sincerely doubt that anyone plays it anymore, given all of the other, much better real-time strategy titles available.
In sum, there is absolutely no reason for you to spend your money on this game when the vastly-superior Company of Heroes is available for the same price. And if Company of Heroes did not exist, there would still be no reason for you to spend your money on this game. Avoid.