I'm a huge fan of the physics system, right down to the subtle feeling of weight sonic has. You can turn sharp if you want to, but you may lose speed if you're not careful.
In my opinion, this feeling of sharp control mixed with a sense of weight is what the sonic franchise has been missing for a while now.
One issue I had is that the button combos were a tad un-intuitive. For example, why is bounce 'hold curl + tap action' when it could just be its own button? I understand not wanting to add too many different buttons, but I don't think jump, curl, and action cover all the bases.
(When trying to gain maximum height against a wall, which uses bounce, wall run, wall jump, and aerial dash commands repeatedly, the inputs are confusing when constantly switching combinations of the same 3 buttons)
Either way, that's just a personal preference. I really loved exploring the physics in this demo and I can't wait to see what you do next with these concepts.