Thinking about it - I visit a lot of phone forums. Every material has had complaints - plastic, aluminum, glass, carbon fiber, Kevlar.
Personally, if any of them wanted to win my heart, they'd have the outer case be some sort of rubber-like material. Something that would grip you back, be nice and bouncy and shock-absorbing on a bounce.
Only thing I've seen close is the Gz'One Commando, and I don't know how many people would be ok with a armored device right out of the box.
But I bet it would save a whole lot of people a whole lot of grief.