Good, but not progressive.
Long review incoming, because I feel the game earned a quality response.
Like most other reviews have said, the game began on a wonderful note and then held on to that one note for too long, eventually it bored me. I finished the game thanks to the story baubles, but frankly I could have happily skipped the platforming parts in the last few levels and felt just as content. It would be simple enough to say, "oh you just need to mix up the game play a bit and everyone would have got along dandy." But then you'd miss out on the true latent potential this game has yet to tap. So lets talk about the real problem, integration:
You're balancing two distinctly separate entities in the game: story and mechanics. The story pops up in the little baubles and the rest is mechanics and the two rarely intersect. At first it seems like we can expect them to interweave throughout the game: the level art follows the story to a small degree, the mysterious spouts of smoke hint at the immediate danger, the mechanic of flight work as a metaphor for the protagonist escaping his past. But these connections never really develop along with the game. And since they don't develop, it's difficult to gain a sense of progression or reward or (all important in story structure) change.
Look at level design, for instance. The larger structures (houses, coffee shops, etc) feel significant to the story. But as the game develops they rapidly become austere and infrequent, largely replaced by tiny floating platforms, which are also quickly replaced by windy gusts and flocks of birds. This doesn't only happen per level, but within each level. Even the first house gives way to platforms in a matter of seconds. Eventually the scenery evokes nothing at all.
I assume this was done to produce a quintessential platforming game. But platforms are only a means to an end, it's the question of where they're taking us that becomes important. I would have been far more interested in exploring (or even finishing) a level if I knew it would lead me to new architecture/story within the same level. For example: imagine if the first level began in the childhood house (provides a sensation and memory of security), led you across a series of platforms (danger), towards Lizzie's house (again, security). This structure gives you two big opportunities. 1- goal orientation, it gives the players a more rewarding sense of exploration and movement. 2- a reason to tell the story through the art. Since you'd actually be going places the platforms can become part of the transition towards the destination. The college level is a good example, where instead of basic platforms you used dorm rooms, classrooms, and campus hallways. These are good sets, they just need to lead somewhere else important.
The level doesn't have to lead chronologically, or even logically (it is a dream, after all), to the next place, but it should lead us somewhere. Which brings up the issue of the fetch quest mechanic.
Again, think about this in terms of level and story design. The point of each level, to retrieve a (by all impression irrelevant) choice of three trinkets, doesn't add to the story at all. The fiery return seems, at first, to portend ominous and dire danger. But after it comes and goes a few times it loses significance aside of its place as a barrier between us and the next level. It doesn't convey progression, change, or even introspection. It's merely a senseless obstacle until the last level. I feel that it's another symptom of the level design. Since the player isn't traveling between important destinations then the unimportant space gets used for a fetch quest because, well, you might as well do something with the mechanics you coded in. But even if you followed this structure throughout, a different change in each level would have felt much more compelling. Something other than fire. Or maybe a transition towards fire.
More to say, but almost out of space. It's a good experiment, lots of potential, largely hampered by level/story integration.