I have an 08 Forester (44,000) and I have to agree that the metal is thin. I have a few door dings and it's sickening. I wouldn't advise using your hip anytime. I watched my wife do this to our (then new) 95 GMC pickup from a distance where she couldn't hear Noooooooo!
I am very partial to several Pontiac Fieros I've owned. That fiberglass and plastic body held up to door dings and such.
I think it would really be cool if Subaru built a Forester with a body like the Fiero and included a diesel engine!