I just got this game today, its a squad based FPS,you be the leader of an elite group of Clone Commandos. And it starts out in the battle of genosis, but your not in the thick of battle, as thats not what the commandos do, it takes place from the end of episode 2 to the beginning of eposide 3. it has the same controller layout as halo with a few minor adjustments, so it's pretty easy to get into if you played any of the halo games, takes maybe 5 seconds to get used to the different controls that are not haloish, like the hold a and use the directional pad to send signals to your squad.
I played through and beat the first level, its a fun game, though one interesting thing as compared to halo, you really cant loose the game unless your entire squad gets killed as they can revive eachother and you. also another neat addition i like is when you melee say a battledroid, oil spatters on your hud for a few seconds before it gets buerned away buy the laser squeegee, not sure if thats what its called, but that's w3hat i'm calling it, various things like blood, or oil will splatter on your visor when you kill things with melee attacks.
If you liked playing halo, and love star wars, i suggest you go out and rent this game at least. I give it a 9.5/10, might change the rating to 10/10 later on when i get a chance to play more.