All of which have plastic:
iMac...Aluminum - Black plastic on back of unit
MBA...Aluminum - Plastic Keyboard Not 100% sure where signal gets through, but there is an opening.
MBP...Aluminum - Plastic Keyboard
Mac Pro...Aluminum - Not sure on this one
Mac Mini...Aluminum - Plastic Top
iPhone 1...Aluminmum - Plastic bottom cover
Apple TV...Aluminum - Plastic top
It has also been proven that the MacBook has better reception then the MBP (go look for thread here on MR somewhere).
Let me clarify that for you all (I just can't believe anyone mentioned it before!):
The Aluminium PowerBook G4 had two plastic "ears" near the top of the screen's backplate, one on each side; the MacBook Pro, on the other hand, has a long rubber strip on the inner side of the hinge, the one which faces the user when the laptop is opened, near the keyboard; The MacBook Air also has a plasticky/rubberish strip on the very same place. They are there, if reports are to be believed, to let the WiFi radio signal through. As for both the iBook and the MacBook? There are no such "special areas" in their casings, for obvious reasons.
Also, both the 1st generation iPhone and the iPod touch have black plastic parts on their backs for the exact same purpose, too... Now, while these 3G iPhone casings could be just mockups, precise in their shape and not in their materials (meaning the final casing could very well be made mostly out of some kind of metal with a plastic part to let the cellular and WiFi signals through), I'm leaning more to the all plastic/Zirconia theory.
It makes sense, since it all adds up:
There have been already four different reports, three of them with photos (two of
white casings, and one of a
black model) and another one with a
crappy artist's rendition (mentioning, also, black, white and maybe red as different colour options), which all match perfectly, down to the little details like their
holes at the bottom or inside the speaker's slit on the front glass. On top of that, there was that
"iPhone Black" slip-up on At&t's website...
I don't know what you think about this when looking at the big picture but, IMHO, all the pieces seem to fit.
