I use the 700 to go to the airport. They don't have a customer service: there is an email address but they don't even open the emails. The driver skips the stops at their convenience. Impossible to see their location, and therefore impossible to know if the bus is early, on time or late. Poor organisation with tickets: I saw buses skipping the stops because the bus was full (with many people that bought the ticket on board) while others outside were waving their tickets at the driver. The card reader on board rarely works so if you don't have cash you might not be able to get the bus. I tried uncountable times with my Irish debit card, another European debit card, and the LeapCard, and it never worked. I saw it not working for other people as well, so it was not me! If you are not in a rush, I suggest you look at Moovit and/or Google Maps and see other options. Also, don't forget that there is public transport that can bring you to the airport at no additional price! The 16 and the 41 are the two buses that cross the city centre and go to the airport. Mind, though, that it is a long journey that might take one hour from O'Connell Bridge.