SmartScreen addresses the security 'hole' that is the user itself. I'm curious about what you are really asking them to address here? I'm not seeing a solution other than for the OS to only run signed code. What OS is secure from arbitrary executables that the user chooses to run?
I agree that it is annoying, but I'm very interested to hear what they should be addressing here.
Instead of throwing up more dialog boxes or making them look prettier or more noticeable or just different they actually need to address the security of their products. It seems like they're just being stubborn and instead of rewriting what needs rewriting they wrap every security hole with new, ever more annoying dialog boxes with every major release.