I have no idea how many people still play Knytt Stories, but my memories of it, both playing Nifflas' stories, and creating my own one, were extremely positive.
A long time ago I posted screenshots, information and even a hand-drawn map about a huge level-in-progress called Non Serviam. Sadly, the game died in development hell, and I don't really know if I'll ever finish it. The truth is, it started out as a warmup for learning the editor, and the entire thing was just added to, slowly over time, in a stream-of-consciousness way, with no real goal apart from the idea that the player would be escaping from a prison and finding a way to free her fellow inmates by going on quests.
The game got larger and more complicated. While I'm confident I put a lot of creativity into it, from a design standpoint it is somewhat confusing, featuring a lot of open exploration, side areas, mini challenges, and extra features such as switches which changed parts of the world permanently, sections where you lose powers and have to find them again in new areas, and a very complicated layout which both the lore and layout just got so big that I couldn't handle it. Some of the platforming is also quite difficult in places (I tried to balance free exploration with challenge, and at least provide dead ends with something nice to look at or experience).
Then my life came apart somewhat, the relationship I was in went sour, I had personal troubles to work through, and the entire thing fell to the wayside. I was creating animated objects based on some of the tilesets I had permission to use, which I later found out was prohobited, which completely confounded me, and that was really the nail in the coffin. Add to that the fact that the art style was a mishmash of other people's work mashed together with my own edits, transitions and botches to get each room to flow into the next (hoping to one day be able to map out the whole thing as a continuous world).
So, what I'm thinking of doing now is just releasing what I have, flaws and lack of completeness included, and then moving on. It's totally unfinished, and I'll have to reset some stuff I put in for development purposes... so playing it might be tricky, but there are probably hours of gameplay in there which, while they might have problems, unfinished branches, poor design choices, and no conclusion to work towards, I did put a stupid amount of time into (largely because back then I spent a lot of time shut away). I think it would be a shame to let that go to waste.
All in all, it was too ambitious, and I was more interested in the escapism of creating a world, than I was actually finishing anything. I think it shows a lot about who I was then, that I was scared of finity, of wrapping it all up and coming to an end. I wanted to just create, create, create and then one day it would magically be finished. Combined with the memories it crystallized around and the unbearable size of the damn project, it just became too much to bare.
I'm also thinking of creating a new level from scratch, or maybe even finishing Non Serviam, depending on how I and others feel about it. If I were to start a new project, I would do my own art and sound/music, and I would set myself some kind of sensible size limit. If there's anything to be taken from all of this, it's never be afraid to start thinking about finishing your project even from the very beginning