I think your doing pretty good. However, in the 'revised physics' demo, there are two things i have a problem with. The first has already been mentioned, you stick to the walls/upside down at too low of speeds to match a sonic game. Another is this;
Waking on water. I did this multiple times, and it seems to happen when you run from the very left of the area left of the green platform, and just running over the water. From there you can walk and stand on the water until you jump, even after you use the teleportation device at the end.
