DK and Peach as characters I feel has the potential to add so much. It's a way of introducing a new play mechanic, that makes sense. Well, more sense then Yoshi transformations (although the car was awesome).
Nitsu: The baby floating is back in this game. Personally, I really enjoy it. It's a dynamic that Yoshi's Island is able to offer that I really haven't seen before. I started playing through it again recently, and kept thinking how awesome the dynamic really is. Most of the time in a game you are "punished" for your inability by either dying, or by the loss of a percentage of your life. This has you physically go back and do something about it. Big difference. Personally it's welcomed. Even though I don't want to imagine baby DK's cry.