Relax, vudu. That video was produced one day after the game was leaked, more as a proof of concept. At that point, the game literally wouldn't work on the Wii. It was recorded using an emulator, hence the slow speed, and the person creating it didn't worry about fixing his mistakes, like the very first mushroom block.
All it did was show it could be done, and that they were working on it. The video above it was done with the released program, which just doesn't seem so good at this point, but is available. Still, it, too, is more or less proof it works, rather than an actual attempt at creating something enjoyable.
The people who made the editor used for the second video based the design off an editor created for the DS version... The difference is, the Wii version can easily be used!
After Reggie is released, I'm probably going to download it and create a few stages of my own, meant for multiplayer purposes, where some players will take a high path, and others will take a low one, and the paths will interact somehow, just to see how it works. Also, I'll be picking up remakes of classic Mario games for the multiplayer, too.
It's a good thing.