I'm no good with video games. But this new super mario wii is great. Thanks to the guide I just solved it like half an hour ago. But the guide never gets you all the star coins. They are however needed. Lots of people have been asking here. Yes it is true you need them all. After you beat the final world 8 guy they show you the ending and them you unlock a world 9. But you can't play any of the levels unless you have all the coins for each level. Like workd 9-1 so you need all the world 1 star coins. At least good thing though you don't need them all just the ones for the world you want to play. But if you want to play them all then it going to be tough.
But at least they are needed. It's finally been confirmed. Incase anyone was wondering what they were needed for.