Their argument is that the cost per seat for the average traveler will go down, and people will be more likely to pack more carefully if they have to pay for the overhead storage.

It sounds like the kind of thing that will take time to evaluate. Some people thought the charge for checked baggage that most airlines adopted would be gone by now, but it stuck.

The ala carte model is an interesting one, and frankly I tend to lean towards it. However, the reality that I would have to pay $30 extra to carry a bag of my clothes on board does take the wind out of my sails a bit.