>are airlines still marketable brands, or is airline travel simply a commodity, with price being the only determinant to a buyer (choosing a route)?

I would say for domestic US carriers it's been a race to the bottom, with price being the only determinant factor. I think for most travellers who might fly once or twice a year to visit grandma, points programs have little value, once they realize they need a dozen round trips to grandma's house just to get enough points to redeem for one ticket. (A ticket that they have to book 10 months in advance.)

For international one might argue there is some differentiation, but in over the past few years I've flown transatlantic on AC, BA and LH, with virtually no difference in steerage, other than a terribly important (to me) marginal increase in leg room on AC.

Cheers,
Geoff Glave
Vancouver, Canada