I guess I would have to see what it looks like first. I think Matte Black would be cool. But one thing I miss though, were the original silver keys. I actually prefer those over the black keys. Not sure how well those keys would look on a Black MBA.
Grass is always greener effect.
I remember getting one of the first iPods and talking to my friends about how cool a black one would be. Then with the iPhone it was the other way around. We all love differentiation. I agree with most of you though, a black one would look amazing.
But if both black and silver were available since launch, I would have probably gone for silver still. Everything else I own is black, tv, ps3, iPad, iPhone. It's nice to have a shiny silver MBA sat on my desk too.