Just got my copy today! 
I would say I'm surprised by how much fun it is, but it's a Mario game afterall. I've gotten over the recycled NSMBW music, because it's actually kinda remixed, plus it almost seems like a tribute to what the New Super Mario Bros. mini series has become so far. Also, I barely notice the music with all the coin noises every second. 
The music was my only initial worry, but now that it's out of my mind I can really appreciate this game. I absolutely love flying with Raccoon Mario, it's really impacted me since SMB3 on the GBA was my first game ever, nostalgia! The coin theme really adds so much extra gameplay to the levels, I find myself doing less speeding through and more exploring and doing everything possible to get those coins. How the level designs work together with the coins, like for instance, a row of coins suddenly appearing near a drop trying to tempt you to take the risk, is amazingly clever.
I've only gotten to World 2 so far, don't want to rush it. I also really like the 3D effect, while not much, it gives the slightest depth and makes the visuals extremely crisp. It's definitely the best looking NSMB game so far, and possibly the most fun..? Alright that's enough of my opinions for now. 
