The primary means of transport around Ireland, and Dublin is driving. Its easier to drive to something not in Dublin.
I think thats the crux of my thinking. Probably flawed but there you go. While I'd love to have the choice of using a train. I think unless you are on a train line already, with enough cpapacity and frequency, you'll be waiting an awful long time to get that anywhere in this country. Based on our "track" record thus far.
I use the train a bit from D.15. In the 20yrs or so I've been using it, its no quicker, its been standing room only for all of that time, stations on route have either no facilities or 3rd world facilities, and my ticket still can't be used for any other public transport on the route. Its still faster to drive, 95% of the time, even in the grid lock. To be honest its actually quicker to cycle my 11/13 mile commute. Considering 20yrs ago travelling and working in Europe as a student, I saw that most of Europes train/public transport systems had all the things we are still looking for here.
Thats why I'm not holding my breath for this world class rail link to Dublin Airport.