I only beat the first 3 levels so far. It was quite enjoyable, the difficulty wasn't that bad, even though I did rage quite a few times at it (but that was due to me being stupid and not noticing the easy solution).
The one thing I hated was the awkward camera. Most of the time it worked fine but sometimes you'd be in these claustrophobic rooms or hallways surrounded by other rooms or hallways and you'd have such a limited range of angles where there isn't a wall obstructing your vision. I didn't notice this problem too much in the levels I beat but it became glaring on level 4 and they did cause me to give up (for now at least).
Other than that, there were some small issues like the goomba enemies' axis of rotation not being centered but that's not as big of a deal (and it might be intentional too).
This was my first 3D platformer and the fact that it didn't push me away immediately from the genre should tell you enough about how enjoyable it is.
Thank you for making this game.