I really hope this Mac App Store fails. If it succeeds to the point that it vastly surpasses expectations, then it eventually becomes the only method of programming and application distribution for a future Mac OS w/ iOS user interface. And an OS that is restricted to a Fisher-Price API subset is not one that I will use. No customization, no 3rd-party hardware, no novel UIs, no cross-platform libraries/development, no X11...hell, the no betas / developer releases bit would eliminate half the software on my machine.
And as for the no non-standard UIs rule, Apple proves to be like any modern government: when you do it, it is illegal but when they do it, it's standard operating procedures.