Think Southwest and you won't be too far off. We've flown on it as well as a number of other European discounters for shorter flights, and we found them all to be quite satisfactory - new equipment, comfortable seats, competent crews, and great prices.

Whether it's worth it to spend more bucks for a more refined experience on a longer flight is a decision for your own spending priorities. If the price was right, we wouldn't hesitate to fly them on a longer flight.