If we're talking æsthetics, I find they all look like silver blimps (glad they're finally shipping darker tones, but it's an affectation). I've seen a lot of dented Macbooks. I don't think they're any sturdier than any other well built laptop, which last until they're obsolete (5 - 10 years). The alu does act as a heat sink, but I doubt it's necessary for the entire body.

I'm sticking with Thinkpads for now, I like the function-dictates brutality of their design and I think carbon/magnesium and some plastic is a good approach for a much lighter result. A Macbook Pro is not only heavy, but slippery. A lot of carbon is used recycling and even shipping aluminum, and the decreasing factor of being able to easily upgrade/repair components. I don't know ultimately what the environmental impact is between the materials, but Apple has advantages of consistency and scale; as much as I like Thinkpads, I don't like that there are a dozen different models each year, which would be impossible to effectively recycle even if they had a program in place.

We're pretty much into a blog here (here's a picture of a beach), but I tried a Macbook, had to return it because of ergonomic factors including weight; I got a pretty great 16" Thinkpad with the same weight as the 14" MBP, I don't even want to think about the weight of the 16" MBP. It's frustrating other top tier companies or the industry can't find a way to have efficient product cycles (Framework is getting there). I guess it doesn't help that Apple has patented their unibody design, which shows how much they care about environment in the larger sense.