I haven't played the game, but having played NSMB Wii and the two DS games, I agree with JayWood about the difficulty.
If one world or the task to collect coins is what makes this kind of games difficult , then that doesn't mean the game is difficult. Overall the game would still be easy.
For me this has been a terrible mistake of Nintendo and one reason I feel this NSMB games have been kinda boring. Adding coins to collect is just an artificial way for Nintendo to say "Look! The challenge is not to finish it but to collect everything!". This has affected the core of the gameplay and not in a good way IMO.
Mario games in the past were memorable because you could die a lot of times and repeat the level over and over. Now they are forgettable because you play them once and forget about them, unless you look for the coins. I rather have shorter and difficult levels than long and easy.
Castlevania Judgment FC: 1161 - 3389 - 1512
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Wii Friend Code: 4268-9719-1932-3069