Surprised that there isn't more chatter about this. I think it is super cool, for various reasons - it's apparently not aiming to be "just another IP tie-in" but rather a different and new way to play, and given the players involved, it will hopefully provide ample opportunity for kids to be creative and inventive with what their Mario "levels" and rules could be. I love how it's taking some elements of the traditional 2D gameplay and bringing them into a Lego "level" that people can build, hopefully however they like.
Mario Maker is obviously a pretty successful project and has proven that players are still interested in the classic gameplay tropes, as well as having the ability to actually build things with them - let's see how much replayability these sets can provide.
Lastly, as an AR developer I'm spending a lot of time thinking about things like "how can a traditional platformer make sense/be fun in a real 3D/spatial sense? What are good interaction paradigms, not only for playing it, but also design creation tools?" It's really interesting to see this take on such issues. Looking forward to seeing what it turns into!
And following that, of course, the Lego of Zelda.