The Wii U's best trick is its lightning fast swap of the graphics on your TV and the graphics on the Wii U GamePad.
The Wii U's worst trick is the absurdly slow loading time users have to sit through when accessing the machine's system menu or any of the applications in it.
I shot a video tonight of the Wii U at its fastest and slowest. This is the best and the worst the Wii U has to offer. Hopefully the slowness will be improved in the future, maybe through a firmware update. But it's impossible to know what's gumming things up and whether Nintendo will or even can fix it.