The Special Report in this weeks Plastics News (April 18, 2011) discusses at length how plastic frames are not being chosen in the popular small electronic products arena (iPads and such). The reason: "...manufacturers favor metal for stiffness".
How this could surprise anyone is beyond me. Flexural stiffness not only scales directly with elastic modulus (and metals certainly beat plastics in that regards except in a few extreme cases) but also with the 4th power of thickness. How can you overcome that? A common trade-off in the plastics-vs.-metals war is the lighter weight of a polymeric materials, but with a small piece like this, the differences in weight are negligible. Another common trade-off consideration is processability - it's much easier to form a plastic piece to some complicated shape than many metals, but the simple, flat shapes of cases makes this also a non-issue.
What really bothers me in the article though, is the attitude in the article of entitlement, such as this line: "But there is no assurance of the future role of plastics in media tablets." I hope this doesn't surprise too many people. It's not like metals are disappearing, are they? (Hint: about 25% of the degreed scientists in our analytical lab are metallurgists.)