That's sort of the point isn't it... Apple is providing a nice little family of style matched devices. Anyone wanna bet the next iPhone and iPod Touch's look like little iPads?
It seems like every few years (maybe a little more than a few) Apple radically changes the design of their products. Remember when everything was glossy white? I'll take the aluminum look any day over that...
Lol I still have my 2g iphone (which is aluminum) and didn't think of that, but for the remainder of Apple products there has been without a doubt a shift away from the plastic enclosures that use to dominate all of their products.
I think that could look good, especially if they can make it scratch resistant with some anodizing and perhaps colors ala. iPod Nano. I've never cared much for the shiny jelly bean look of the iPhone & iPod Touch.