Just saw the new trailer, and I'm sold on the backgrounds. They do look different enough from the last two NSMB games. I love how some of them are animated and they're all pretty unique from one another. I love the "Starry Starry Night" styled one. A lot of the foreground looks nice and distinguished from the old games too; even the ground you walk on looks nice and new.
However, Mario, Luigi, the two Toads (which I'm sad to see), the goombas, koopas, the coins, the water, and those little dancing flowers all look just the same as they always have (not surprisingly). I hope they're just placeholders or something because It'll be disappointing to have recycled character models in these all new, smooth surroundings.
But there were some cool new stuff. I was NOT expecting the baby yoshis, and they were a pleasent surprise. I like how they're able to do things besides eat stuff and grow into big yoshis. I'm REALLY happy, however, to see the acorn power-up, not necessarily because of the flying squirrel power, but because they've finally introduced a power-up that's NOT in the form of a mushroom or flower, The only other ones I can recall were the leaves in Super Mario 3D land (borrowed from SMB3) and the ones that are literally suits.
Overall, I'm impressed. I wish I could say the same for New Super Mario Bros. 2 for the 3DS.