Oddly, I learned about this because Bandcamp told me about the score showing up there.  I saw the soundtrack with a link to the game, and had to play it.  I pulled it up, and thought it was the cutest thing ever.

Then I started playing; 15 minutes in, I had pretty much met Granny and failed to make more than one or two jumps without falling due to mis-alignment due to the terrible camera, and the fact that the z-guide is pretty much useless unless you're currently over ground, and the hard parts are all when you're not over ground.  I quit and was extremely disappointed that it didn't live up to my hopes.

I came back the next day, and after another 15 minutes or so, was starting to get used to it; I still failed the vast majority of jumps I attempted, but could make just enough to feel like I was making progress.  I then discovered that the d-pad works as well as the joystick, which made climbing on walls bearable since I wouldn't randomly move sideways or up into a spike due to very slight misalignment.  It wasn't great for 3-d platforming, due to slight camera skew (though that may have been "fixed" in 1.1?  Not sure what that bullet point means, and I just saw it exists before posting this).

After a couple more days, I had 26 berries and was feeling pretty good; there was still some fighting the controls at points, but it felt more like a Getting Over It style "hard and sometimes broken controls but mostly fair" challenge rather than the initial "impossible controls make this a broken game".

And a few minutes ago, after 4:45:32.712 in game, I got the thirtieth berry and my clock stopped, and am sad it's over.

Still, some major frustrations.  As noted above, the z-guide is useless when you're not over ground, which is most of the hard jumps.  It's not always obvious how high you need to be to grab a diamond to get the second jump, and there was often some trial and error to figure out that height.  And on the last berry (my last one, and to say it without spoilers, what would reasonably be considered the "last one" from a "plot" perspective), I was still missing the very first jump about 5-10% of the time, and the next trick probably about a third of the time.  This was after getting that far probably about fifty times; the fact that I could do a trick that many times and still fail it frequently is kind of unfortunate.

That said, there were also several more beautiful moments that made me smile even more than the initial entry into the game.  One berry was a nice puzzle of "I think I know what I need to do, but how?  Oh... If I... yeah, that'll work."  And then took two tries.  A "hidden" berry that made me smile.  And one final one, that I might say seems unfair.  But the pure joy of going "huh, I wonder..." and getting the reward justified it for me.  I might have spent hours looking for it and gotten frustrated, but just wandering around the map looking for the last few strawberries worked for me to notice an oddity and get the berry.  And I thank the developers for putting it in.

Also, one of my major complaints was apparently addressed in 1.1: Stop wall climb hop onto spikes, or wall-climb rotate onto spikes, to behave like original Celeste. This does not stop you from climbing into spikes on the same surface as you.  The number of times I was pushing forward to land on a wall, only to land on the top and immediately climb into the spikes...  that change probably would have cut 15-30 minutes off my completion time.  Oh well.

All in all, while it's certainly more experimental and less polished the Celeste and Farewell (and even the Pico-8 Celeste and Lani's Trek...), I find this a worthy addition to the Celestiverse.  I'll likely replay it a few times in the next few years, and hope for a more complete game if the team can figure out how to sand off the rough edges and make it a bit more friendly.

edit: One final thought: the feathers didn't feel nearly as bad for me in this game as in Celeste proper.  I realized it's because feathers are normally annoying due to the full-circle freedom they give you as compared to the normal precise 8-directions you get in the rest of the game.  Plus, the time pressure means you can't just take it slow and nudge a bit at a time.  But here, the entire game has that full-circle freedom (and often time pressure of falling platforms), so the feathers fit in better.  Funny how that worked out.