I haven't flown them. But I do admire AirTran. They have a premium cabin, for instance, which is nice. You can pay a good deal and buy a "business class" ticket, and have a fully changable ticket, or you can by a coach non-refundable ticket, which unlike the majors is not a "use it or lose it" affair, as it is with Easyjet.

And AirTran does use a hub and spoke system for many flights. They even make a profit!

I think the low fare airlines like Easyjet are cherry picking the city pairs that make them money. Clearly there are tons of city pairs they will never fly, and therefore room for the "majors" or for low fare airlines more like AirTran than EasyJet.