I thought the optical drive was the limiting factor for thickness. Has a manufacturer come out with an ultra thin drive recently? What are the ultra-thin PC laptops using, if any?
I haven't really seen anything thinner than MB/MB Pros, which are already just 1 inch thick while still having an optical drive. So not so sure how they can make it any thinner. But there are lots of Japanese laptops w/drives that are significantly lighter, but they are really expensive ($2000+).
I think it's a really good thing that they're bringing the 12in size back. My cousin really loves hers, and I know there are many others from reading the posts here on MacRumors.