For people who can't decide, here are my opinions:

Don't get Wii Party U. You can get it for $50 at the store, which includes a Wii Remote Plus, and Wii U Gamepad stand.
If your into Mario, and don't already have NSMBU, I recommend getting this cgame.
The other two are what I recommend the most, Pikmin 3 and WWHD. Both are fantastic games. For me, it's just mainly me choosing which game I want to buy in a case or to get as a download code.

I am getting Pikmin 3 for the deal.

I got Mario Kart and I got NSMBU as the free game. At the same time I bought Injustice: Gods Amongst Us as it was on special offer on eshop. So I spend many hours this weekend on my Wii U. Guess which game I've been playing the most... Injustice.

I'm sure MK8 will last a lot longer and I'll still be playing it months from now. But I'm not excite about another incremental update to Mario Kart. Finding the story of injustice quite engaging.

Would say I'm pleasantly surprised by NSMBU. NSMB2 was a let down and NSMBU got a lot of criticism for being more of the same and my expectations were low. It's actually very good so far. Good level design, great overworld map, nice music (both remixed old stuff and new stuff), and quite pleasant looking with nice backgrounds. I also enjoyed playing through some of the speed run challenges.

It does have the same old boring bosses. When I first saw the small ship which looked like a koopa kid I thought there was going to be an interesting boss fight. Sadly that wasn't the case. Is there a rule that only 3d Mario games and yoshi games can have good bosses? It's especially sad because when I think of Nintendo games I think of big and interesting boss fights and seen in Zelda, star fox, 3d mario and metroid.

In the end I got NSMBU because I dont have the game and it was also the smallest game in offer so my HDD lives for another game

Got Pikmin 3, but who knows when I'll get around to playing it! xD

Ended up selling the code, I'll buy a retail copy of W101 to add to the collection later.

In the end, Mario Kart cost me $20. Not bad at all.

Pikmin 3! It took me a while to figure out how to download it.. It wasn't as intuitive as u thought. I hope it doesn't deter the cazuals.

We did Wii Party U. It was the only one we didn't already own. We already have plenty of controllers and some how never bought any of the prior party games. Crazy omission when you think about it.

At work we got the Wonderful 101