Great stand alone, but not expansion
The multiplayer is great because it plays like and FPS, fast drop in and respawn, none of this waiting 3 hour for a game with a friend to end and then having a player drop 30 minutes in. This game is action to the end in any multiplayer battle. It is a staple at my lan parties and I've got copies on all of my pcs, well the ones that can run it. IT runs on most older and cheaper PC's and even looks great with a built in benchmark, but I have had a few friends laptops that could not run it.
If you do already own World in conflict I suggest Men of honor, or supreme commander gold, both are also available for around $20 fairly often online.