I will reiterate what I said earlier about the choice here by HP. You'll hear it from their mouth on Monday as I interviewed their VP of Mobility on our podcast.
Points are: They did not use metal to (a) keep the weight down (b) the material looked good and does not scuff (c) if it breaks the part is replaceable (d) it does not interfere with the antennas, which they worked very hard on due to the focus of this device
After a month of daily use, I still have no negatives to report and think this is some armchair engineering going on here. In short, the detractors here are just wrong. Not an opinion, you're wrong on this.