Ok so I am picking things up from all the gameplay demo vids being released.
First off I am looking more forward to this than anything, its wonderful. I mean its Mario and it is sexy. It is 3D and it is doing new things
Now something I am finding is that it is picking up a lot from other mario games and I will just talk about a few first
Super Mario Bros. 3 ship song: played on prologue, played when you jump on the ship in stardust galaxy
Super Mario Bros. 3 1-4 level song: In the galaxy of cakes and stuff.
IMO: The whole bringing back the ship theme rules. Its where bowser belongs and It is the sex!
Power Mushroom: The typical mushroom (mario's first and most famous power-up) makes a return in the form that it ads on another health gauge. You aren't getting bigger, as that ended with 3D platforming mario. But it finds its spot.
Luigi: Luigi is definately in it, I can prove this with a video. Here
I do not know if he is playable, but I imagine they are trying to bring that back...
Post things you've picked up on that any real mario fan will love seeing.