While it doesn't detract from the sheer awesomeness and expansiveness of this game (in the form of new powerups, a better hidden and optional star system, as well as more fun and interesting challenges in each level) it does make it frustrating for those who want to clear the game 100%. Yes, that would be me. But I refuse to do it in this game -- or at least, I refuse to work hard at it and will instead slowly accumulate stars until I may or may not get to the full amount.
And that's about it. Graphics? Amazing. Story? Hahaha.
I might add that as proof of my above claim, I cite the number of times in this game I have said "Oh I was lucky that time" in getting a "difficult" star -- I got some of the really tough stars already and missed some of the easier ones simply, simply because I was off that day and couldn't pull the particular stunt. I don't think that happened to me a single time in the first SMG.