This game really worked for me. The physics was very solid, and in the early part of the game, while learning the controls, I felt like I was getting better and better at swinging. I had a real sense of mastery while playing which was very pleasant (and an experience that is generally quite rare in physics-driven games as it's difficult to design complex simulations that are reliable).
I found the leap of faith level too difficult to complete, I couldn't tell how far apart the branches were because of the camera angle, so I'm not sure how close I came to beating it (I got to the third last branch).
The arms are the only thing I'd really suggest to be improved. I'm not sure where the forces are being applied, but the arms seem to rotate around a bit weirdly, as if the force were being applied at the elbow. I found myself missing a lot of grabs because the elbow was bent in a weird direction at the moment that I needed the arm to be outstretched.
I was also very impressed with how stable the vine climbing was and how intuitive it felt. (Like I felt like an actual Monke)