I was really exited about the Wii U up until the press conference yesterday.  It does so many things that I really want, like being able to shift the game you're playing from the TV to the Wii U Gamepad screen and play it directly from there.  Yesterday I was playing Darksiders and my wife wanted to watch TV instead.  This happens all the time in my home; if I could just shift it from the TV to the Gamepad, I'd rarely need to quit playing so I wasn't hogging the main TV.
I'm also excited about new ways to play using the second screen, achievements in Wii U games, online play and the social aspects they're integrating.  The problem is, they didn't show us any significant killer games to go with the hardware.  Some footage of a new Zelda or Metroid would have been great.  I had my fingers crossed for a huge reveal like new core franchise to go with the new hardware.
I really want to like the Wii U, as I'm a passionate Nintendo fan, but Nintendo has got to show us more than what they've shown so far to get my to open my wallet when I already have a TON of games in my backlog.  New minigame collections and ports of games I can already play on my XBox360 don't justify the purchase.  I hope they have more to show at E3 before all is said and done.
PS. - Zombi U does look pretty great though.  I LOVE the idea of using the gamepad to input a door code while you can see the reverse view of zombies closing in on you from behind on the main screen.  Such a great idea!  I hope to see more fresh and creative uses of the second screen like this.