How about multi-boot? From my understanding that isn't going to be possible anymore.
And theoretically, Grub (or something) can have the key signed.
More importantly, how much would this sway a decision of a consumer (one place where I find 'consumer' better than 'customer') who sees two similar laptops with very similar prices except one say "With Windows 8" and the other says "Windows 8 Certified".
Could the manufacturers not come up with their own marketing campaign or something like "OpenSource Initiative Certified" or something like that[obviously they can't use OSI's name but you get the idea].
And you dont think that is a political choice?