I have an Abbey Electron card and I use it only for booking flights, trains etc. online. There is no money in it, I just transfer it across online instantly and save a fortune!
I have flown with Ryanair on 22 bookings during 2008 which I think means I have saved over £100 - please correct me if I am wrong. Coincidently - I haven't paid more than that in total for all the flights!
I know many people don't like paying the extra fees. If you have baggage - go with BA etc. If you don't FR/U2 are fantastic!