Along with Project P-100, one of the biggest surprises at the Nintendo booth at E3 was Game & Wario. I would have definitely been less disappointed with Nintendo's on-site press conference if they had made some mention of either game.
That said, Game & Wario was far from a showstopper, and that's coming from a huge fan of the WarioWare series. The games here appear much longer than those found in WarioWare, and they generally lacked the humor and the punch normally associated with the Wario name. The game with the arrows and the stomping was pretty fun, but the others felt rather tame, especially compared with the surprisingly exciting times I had with Nintendo Land.
If Game & Wario ends up having 50+ mini-games included, like a traditional WarioWare title or Rhythm Heaven Fever did, then it may end up being a must-have purchase. If it only includes 12 different games like Nintendo Land is planned to, then it may not have what it takes to win your attention.