I'd just have to second what Avichay said, with the addition that I've used Ryanair pretty often, and not Easyjet, purely because Ryanair flys from all the airports nearest me, and EJ doesn't.
The prices are rockbottom, especially if you can book ahead of time, or risk picking up a seat on the day (I recommend against the latter, you can often get on the plane just by paying the airport tax, but then again, the flights are often full.)
They're not posh, you won't get fed, or to pick your seat and they cram the passengers in. It's pretty much just like taking a bus, just faster, and sometimes, cheaper. I've taken flights to the UK where the bus shuttle into the city cost twice what the return air ticket did.
