I'll give it a good six months before I buy one to see what issues come up. I'm more worried about flex than the shocks and vibrations it would be subject to on my commute. I've had a powerbook almost completely apart and the only component that I found to be protected from shocks is the hard drive. It's mounted using rubber grommets. The Macbook Air has an option for a solid state drive which would help in the durability department but it's small and expensive.

Mobile phones and iPods are pretty thin and probably subjected to more abuse than a typical notebook so while it's something to consider it may turn out to be just a durable as a Macbook Pro.