You can fly from Boston to San Francisco in JetBlue's premium cabin, which they call Mint, for $599 one way. Not bad, particularly if you're going at short notice and you're being forced to pay walk-up pricing anyway. Six hundred dollars is pretty good for a lie-flat seat, nice food, and a private suite if you're traveling with someone.
I compared this to my benchmark transcontinental premium class offering, which is on Cathay Pacific between New York JFK and Vancouver. It also offers a lie-flat seat in business class, but it's $2,935. (It's an international three-class aircraft, so it also has an even nicer lie-flat seat option in first class for $3,732.) So the JetBlue offering is a pretty good deal, for what it is.
I hope they're successful. I don't generally fly in the premium cabin, but that pricing is within reach for a splurge.
(I own no shares in JetBlue and have no interest in the airline other than as a satisfied customer.)
JetBlue's page on their premium class service.
Cathay Pacific's page on their business class service.