Ok, I played the demo, trying to improve my Pika (:D) and I noticed somethings.
Nr 1: Bowsers' Up B is way to cheap. It comes out way to quick and is way to powerfull. It cries for a nerf.
Nr 2: Pikachu needs some improvement. I don't now what, but I'm rly having a trouble killing with him, atleast against the heavy characters. The smash has big start-up lag. I'd recommend nerfing the lag and dmg on that, or give another move to help him edge guard or something. The thunder is great though, you balanced it well :D
Nr 3: I think you should maybe change Marios' airial to the uair instead of the spike, It would help him combo in the air instead of being cheap with the cape ;P
That's all. I don't want to kill your spirits or anything ;D, but I think it's better to be critical and give you things to think about, rather than having trouble with something in the game, and then be quite about it because you don't want to hurt someones' feelings or something ;P
Yea, that's all. So long and goodnight! :3