Actually, they are having a one pound sale. No catches as long as you are canny.
If you check in on-line, have no hold baggage, have only one carry-on item, don't buy insurance, don't ask for text notification of alterations to the flight, don't want to get priority boarding, and pay by RyanAir's own charge card or visa electron, it is indeed only £1.
There is no compulsory check in fee. And for tickets booked on certain £1 flights there are no airport taxes. I just booked Chris flights from Luton to Knock for £1 each way.
Vicky