Gonna be honest, I went in pretty skeptical and didn't enjoy it much at first, but it really grew on me!
The character is difficult to control and at first I didn't feel in control at all. It took me a while to get the hang of it but once I did it became very satisfying and fun. I still sometimes feel the character is overly "sticky" and it's hard to make precise jumps but when flinging up shafts and between walls the stickiness is appreciated. Maybe it needs some tweaking but the basic mechanics work well.
I think the only reservation I have is that I'm not sure how well things will work if enemies or hazards are added. It's relatively easy to get where you want to go once you have the hang of it, but still very difficult to make precise jumps. I think if you're approaching this as a mechanics demo/test that would be the next thing to play with.
I found navigating the level to be insanely confusing and didn't finish it, but I understand this is more of a mechanics demo and that isn't really the focus.