I noticed a bit of an error when the person hits the edge of a block and the persons feet are just on inside it, instead of the path. When this is done at the right angle, it lags the person up a bit and can get stuck.
@ leewaysleo, the game runs smoothly for me under 40/fps. No lag what so ever, in fact, this game is one of the smoothest ive played for a while. But there is a bit of lag when advancing to (especially larger) maps.