Super Mario 3D World is a great game and will certainly boost the Wii U's popularity. While I didn't find the game up to par with the quality of the Galaxy series (especially in terms of single player experience,) it is the best game on the Wii U, especially if you have friends and family to play with.
The cat suit... Well I had my doubts and they were well-founded. Prior to the games release, Miyamoto said that the cat suit would not only introduce new dimensions into the game, but also make it easier for people who can't quite master the platforming. If that sounds like dumbing down to you, then you are right because in many levels the cat suit absolutely makes the game a snore. In others it introduces many new ideas, but more often than not it makes certain levels ridiculously easy and renders classic mario platforming obsolete. And while it is quite and cuddly, it often just seems lame.
Speaking about lack of difficulty, this is easily the least challenging mario game to date. Yes, I understand that this game is partially made for kids and families and multiplayer - and therefore HAS to be quite easy - it was still upsetting at HOW easy it was. By world 4 I had over 50 lives. This lack of difficulty takes the challenge out, and certainly makes one ups and power-ups completely worthless. Because of this, I simply cannot recommend the game to anyone planning on playing it alone. That's a shame, because there are a many, many levels with wonderful designs and ideas, but only a few offer a challenge.
Thankfully, the multiplayer saves it. I won't mention too much about it, except it's just mad mayhem and works very, very well. It's optimal to have 2 others, for a grand total of 3, to have a lot of fun without running into camera problems.
Nothing to mention about the story, as usual. But the graphics are better than ever before. The sound is great too, though not up to Galaxy level. But then, not much about this game is.
Overall, it's a solid game and a great one if you are playing multiplayer. Less abundance of lives and not so many darn cat power ups might have bumped up the difficulty, and bumped the score up to a 9.