Yeah when you're done with the game you can freely save when you're on the map instead of only when you open up paths and such. There's no real reason to save the star coins until the very end. I used them as I went along the game. Then again I was beating collecting all the star coins and beating stages with multiple endings as I was playing through so I always had more than enough to spare.
I actually didn't think this game was that fun...it was more addictive in the sense that I'm a completionist. Whenever I even start a game I want to beat it completely with a 100% rating. The "bosses" were all the same. I do understand it's for kids but I thought there might be some more fun-factor to it for the young adult crowd. I guess the only replay value is the mini-games.