I love the idea behind the movement. Wall runs/jumps, gun jumping yourself into the air, grappling. It's all very cool. One thing that would make it feel less slippery and more in control is greater air control. There's already some. When grenade jumping, you can slow your movement forward by turning the camera sideways and pressing A or D in the opposite direction of the jump. But you can't slow down by pressing S, the "back-yourself-up" key. I think air control would go a long way into making the game feel more in control. Currently I feel like a drunk man when I'm jumping, or even just running. You can kind of air-strafe, but the control isn't there.
Also, I feel enemy ragdolls should lose collision when dead. In the first sky level, I ran into an enemy to keep him from shooting me, and I lost all momentum and got stuck on the ragdoll such that I had to go backwards to get around him. It wasn't a good experience.
It would be nice if I could hold spacebar when jumping and not instantly bounce off a wall after jumping into it. Maybe have it wait till I press jump again for me to jump again instead of having me bounce again after holding space down once. It would make the controls tighter.
I don't like getting launched off the level from a grenade launcher wielding enemy. I'd rather just die and restart since getting launched off the level will end in the same result, but more S L O W L Y .
Some people have expressed hatred towards the milk table, citing that it slows down runs. It does, but if you just improved the air control, people could more consistently jump and steer into the milk instead of hitting the table and carefully lining up a jump to get that milk.