I use low cost airlines when they are cheaper, but it's not always the case: sometimes it is much cheaper to take Iberia, Air France, KLM, British Airways, etc rather than Ryanair, easyjet, Vueling, etc... and of course the service is MUCH better outside lowcostland.
Low cost airlines are now charging for luggages
, for paying in VISA
, etc, etc...
I think Low cost airline can survive IF and only IF they sell tickets at lower price, otherwise the will go to hell
Anyway all the low cost are struggling more and more at the moment, and it will be even worse as soon as winter comes...