This game is good because I didn't buy it.
It is set in the Star Wars universe.
You get to pilot little vehicles in vehicle mode.
You can be a Jedi in little man mode.
Vehicle mode is fun.
Little man mode is not.
That, in a nutshell, is Clone Wars.
The campaign is fun to play through a few times, even though it is highly scripted and somewhat easy. Plus, the campaign lacks co-op. However, the multiplayer can be a huge source of enjoyment. I haven't got the chance to play the game online when it came out, and I just got to play it in January. Nobody was on. So therefor, I can't give you the rundown about that. But, to be honest, this is the seventh generation of gaming. People have moved on. Want multiplayer? Buy Halo 3. If you want this game, don't worry about the online aspect. Chances are you will be the only one in America who will be if you buy the game soley for that reason.
Instead, go for the off-line co-op little man mode, or 2 on 2 vehicle deathmatch mode. Those are fun. Or, take a spin in the campaign.
To be honest, unless you are really interested in this game, don't even bother tracking it down. There are better games to find, and this one really only amused me because it came with the Xbox my parents purchased me for Christmas. If I had bought the game, I probably wouldn't have liked it as much.