Without a doubt, Cloudtop Cruise is definitely already my favorite and most anticipated track in this game. Bowser's Castle and Dolphin Shoals are a couple of others in particular, although it should be known that I'm more-or-less excited to play all of the new and retro courses alike. I might also add that I am very much enjoying and am impressed by the soundtrack of this game (specifically, the new original songs). As someone who listens to a variety of Jazz on a regular (Jazz-Hop, Nu-Jazz, Smooth Jazz, etc.), from the little I've heard (Dolphin Shoals, for example), I've already come to appreciate the direction that of which this game's OST is taking.
If DLC does in fact come our way in the near-future post release, I do hope that Maple Treeway will become an additional select retro course to be revisioned. It being my favorite course for one, but just for the beauty I can imagine it would bring, what with the graphic fidelity this game has presented.