the second player's role is much larger in this game than it is in the last game, which is great because in SMG1 all you did was point at shit and it was still super fun! i have not yet played as P2 myself, but yesterday my friend and i played for quite a number of hours and the way she helped me made me kinda confused as to how i would have beaten the level by myself (it was the one where you have to lead all the giant chomps into holes). the second player can get coins for you, and 1-Ups, and freeze enemies as well as just fuckin' kill them while mario just runs around freeloading.
but god, this game is way too much fun, i just started on world 5 and i am still experiencing moments of disbelief where i just cannot believe how much creativity the mario galaxy people had left in them after the first one. music's wonderful as well, as expected. and i have only 50 stars out of 240... this is going to be a good start to summer.