Nice, not what I would have done, but I like it.
As soon as I saw them together, I knew I wanted black keys on the white topcase. And to actually have the USB hub of the HHKB Pro 2, I needed to use the black bottom. I think this looks slick.
Now, the white (and gray) keys on the black topcase? Well, that's just the crap left over (kinda like Danny Devito in "Twins").