there's an error on your demo. When you try to start playing, the starting map is not defined. plus on the 2-1 Level, when you press down, an error appears, "Missing SpriteDef Taunt" and your gravity is set to 0 (unless you wanted it that way)
otherwise, everything else runs very smoothly and i like the addition of other characters. with the Demo version you should also include some (not all if you want) the help files, like just the movement directions.