It's pretty cool.  But I'm waiting for Mario Odyssey!  I'm more into exploration based Mario.  :)

I just unlocked the Mario 3D world panel in Mii Plaza. That's pretty cool. 

yeah. i finished 3D world main game in like 3 days, but need like 40 more stars for final castle. I've been going back to previous stages to find green stars. Still fun replaying early levels. Very clever and creative ideas at play. Looks really good. 

My wife and I did everything in that game and even played all the post-game content, which we almost never bother with. So much fun! And Bowser's theme is awesome.

Is it a 3DS title?

No. It's a WiiU title. It's basically a sequel to the 3DS game that had isometric 3D stages. Not really a fully 3D explorable game, more like bite size Mario 64 levels the length of an average 2D mario stage roughly. Game looks REALLY good on TV, but I've also been playing on gamepad like a giant gameboy.