One thing I must say is tricky is that going uphill and then hitting a flat area can be brutal. However, the ball physics in that respect are quite fair overall.
I would have loved to see some SFX or BG music in this however. It all seems so clinical and void of life because of that. Some simple bump sound effects etc. would have really contributed in a positive way here.
One little gripe I had was with the matt surface glare from the light source. At times on cerain maps the platform would go from completely clear to completely washed out. Which means you're often fighting the camera angle as well. Other than that I loved the level design and the way certain sections of the maps are 'hidden'.