I did not book my ticket online prior to using, but thought that it was not necessary to do so. The location of the bus stop at Dublin airport was right off Terminal 1 and easy to find; purchasing a ticket and getting a bus was another, unfortunately. There was a long queue for boarding the 700 bus going into Dublin City centre, and I was told that until the current waiting passengers were put on an arriving bus, I could not purchase my ticket. But my main complaint is that the bus does not arrive every 15 minutes as advertised. This was both for my trip from and to Dublin airport; I waited close to an hour for both trips. I was fortunate to have allotted a lot of time to get to the airport, otherwise I would have taken the other buses or taxi that kept passing me by. The trips however were smooth and easy, and the bus operators were professional and friendly.