The hitboxes feel really unforgiving! I spent way longer than I would like to admit on trying to beat this game and often died when I felt I shouldn't have, things trying to fall past a bat and dying because my white outline brushed against his wingtip. Though I also shoved half my head into a bird's belly at one point and didn't die, so I'm not sure what's up with that?
I agree with the others that the directional dash thing just made things harder, as it meant I couldn't jump while adjusting my position. But you've already heard about that, so instead I'll say: it's a big problem that the ending dog is placed in front of the enemies. I died multiple times because of that thing hiding an enemy from view - and even when I beat it and sat with my owner, starting to scroll off the top of the map (by the way it seems you can do that), I ended up floated into an enemy and killed! That's just not right!
I also got killed by bats in the space section due to not seeing them in time, as ... well, they're black, the background's black, it takes a moment to parse they're there. It may be good to give the enemies some kind of outline (just not a white one) so they're easy to see against all backgrounds. Also the balloon is a death trap in disguise.
All that aside though, the graphics are adorable and so's the music! I'd have preferred a little jump animation to the current spin, but I love the gradual dithering to different colors and the overall visual style is super cute. It was easy to tell powerups from enemies and having three jumps per jump gave me a lot of freedom in scouting out what was above me and choosing where to bounce from. And the fact I played this thing for so incredibly long without giving up, well... That's gotta mean something.