It was pretty fun! We're kind of rushed through, so it's hard to get a great grasp on how intricate or how much hidden stuff there is. But the levels I played had interesting elements to it.
I'm always disappointed with how horizontal these levels are, but I also feel like I'm misremembering how vertical the older games were. I don't think this game will be very revolutionary, but I'm thinking it'll still be lots of fun.
Edit: Come to think of it, I think it's Yoshi's Island that is making me think Mario levels are more vertical. That game went all over the place.