My own feelings on Super Mario Maker are that it's an excellent start, but is missing many features that I hope to see be partially rectified with DLC.
You can't even make slopes, despite 3 of the 4 game styles that are featured here having had such a component in their original forms. And no vertical levels past two screens in height. And many an enemy and other features from the 4 titles modeled here are absent.
Also bring back Mario Paint's sound system. They sort of have something now, but the template for what they should do is already there on that SuperNes classic that inspired many other aspects of this game. I wouldn't have the talent to make use of it, but many would.
And I have a feeling that the lack of a checkpoint system is really going to stink on some of these difficult user-made creations.
My impression from the review was the included levels were haphazardly organized and didn't compose a conventional game progression.
I believe you're essentially correct about the included levels.
They're laid out in a world system with 17 worlds, but they don't have the cohesiveness that traditional entries had. They're more for demonstrating the possibilities at your fingertips with the level editor and to provide a way for you to immediately jump in and play, rather than an attempt to create a full fledged traditional sequel.
Similarly, fan sharing was also not particularly organized yet and didn't seem to offer a way to find anything more than random levels. No good ratings, "cultivation" or creation of "games"
There is a rating system in place for level sharing (And a system to provide direct feedback).
And if you particularly liked a level, you can select to follow that editor's creations to easily locate his other offerings. Not sure if Nintendo will do all they can to cultivate the online end of this, but right now, probably the single biggest issue with sharing is you can't create and share your own game.
The best you can do is follow someone. So if they're recreating the original Super Mario Bros. for instance, they just have to clearly label each level. Then by following them, you can easily download each individual component and assemble it yourself.
Everything I've seen about Mario Maker looks awesome but I just don't have the time for it.
If it's the level editing aspect of this that interests you, but you feel like it would be too time intensive, I think you'd be surprised.
It's incredibly user-friendly and intuitive. There's essentially zero learning curve here.