Hi guys. I got my Wii back and I'm back to doing fun things.
OK so if you dash toward and edge and then hit up+b and IMMEDIATELY wavebounce back, ZSS will up+b off the stage and slide safely back onto it, spiking anyone above her without putting you in danger. If done correctly you will not hear the sound effect usually caused by up+b (well sometimes). Zero and I were talking about it on IRC for a few minutes and it seems marginally useful.
http://www.youtube.com/watch?v=yUR_yUlZVFQ Video
Yes I realize this is the same principal as capedashing but whatever. The more you know.
Up+b also allows you to reverse the jump caused by hitting X or Y on the edge and carries your momentum when you run off platforms causing you to glide to the ground instead of falling.