My point was that Apple considered the products to be acceptable - even more so, the 3G was a plastic-backed successor to the aluminum-backed original iPhone, so Apple saw it as an improvement.
Therefore, to say that plastic is inherently bad or "cheap" belies Apple's own product line.
The 3G, in particular, shows that Apple considered the move to a plastic back from a metal one to be an improvement, and they stuck with that for years.
Therefore, to attack the Nexus 7 because the back is plastic is to attack Apple for using plastic.
The Nexus is more comfortable to hold, and for that reason, I find the plastic to be superior.
I've had a lot of aluminum MacBook Pros/Airs. I love the unibody design, but the aluminum edges are painful. Sometimes, pretty isn't pleasant.