Ooh, not bad! I think if you were to flesh it out, this would make for a pretty fun game, as well as a very unique type of platformer. Perhaps you could have to control each leg individually, or make it so they don't slide across the floor. I understand this is just the bare features, but I can see you adding moving platforms and all these things that would make the game more challenging, or perhaps like a puzzle, like trying to carry a box to the end of the level through obstacles.
If you think you can make it into a full-on platformer and/or puzzle game or whatever you're doing with this, go for it! I personally would love to see a ragdoll platformer game made with the Joints extension.