Got the Wii U/MK8 bundle this weekend. It's quite a step up from the Wii and the game is brilliant! Love the anti-grav. The Mrs is hooked on it! Definitely a good buy. Just need some extra controllers for parties now.
Mount Wario is awesome! Love the fact it's linear. But, like you say, all the new tracks are stellar. This feels by far the best Mario Kart yet. I even like most of the updates to the old tracks - but wish they'd just made more of the new ones, because they are simply sublime!