I just came back from E3, and I want to give my impressions on the game.
I'll save some time by saying I was really impressed. I know we saw the new trailer with improved backgrounds and such, but you all really need to see the game up close in motion to fully appreciate the difference. The animation is considerably improved and everything feels amazingly smooth. I don't know if the Wii U is capable of AA, but there was no aliasing whatsoever on the demo I played. One of the biggest problems with NSMB: Wii (which I suppose, to be fair, can be said about most Wii games) was that it amazingly jaggy, which made an already not really impressive looking game look even less pleasing. But NSMB: Wii U doesn't have that problem thankfully and looks all the better for it. While the NSMB games are obviously the base, the game has so many improvements in so many different areas that it almost feels like a completely different game.
As for the gameplay, the physics and controls are, unfortunately a lot closer to NSMB: Wii than the graphics were. The only new things so far are the squirrel suit, which is actually cooler than I thought it'd be, and the baby yoshis. The squirrel suit functions as basically the cape and raccoon did in SMW and SMB3, when it comes to slowly gliding down. It also gives Mario the ability to stick on walls for a few seconds. Baby Yoshi isn't particularly interesting. You can inflate him by shaking the Wii control, and he serves essentially the same purpose that the propeller suit had (except you can shake the control several times before he runs out of air). Fairly meh but whatever.
But overall, I'm SIGNIFICANTLY more excited over this than I was before today. Game's gonna be fucking AWESOME.