I love platformers, so I had fun with it. I like the music and I do feel like there's some potential with the shifting between characters.
However, I'm not sure that the wall jumping was working properly for me. Or maybe I was just doing it wrong, but I couldn't seem to jump off of the wall. Any time I tried my character just kind of fell off the wall, which made the final level incredibly difficult. Speaking of which, I think you maybe need to make the walls on that final level a bit taller, because you can actually just jump on top of the level and skip everything.