Just got back from 8 days in early October
(see my post on the Hilton board about the Conrad hotels)
My recommendations as to what to do would be tempered by how much time you have to spend.
It was our first visit and the trip was somewhat disappointing many due to the fact that we did not get to see even half the places/things we planned to visit.
First off driving in Ireland is no picnic
(they drive on the left, but that not a problem for me)There is absolutely no motorway system, look on the map, plan to go 100 miles to say Galway 2 1/2 conservative right?? Well its going to take 5, because you are going to be through dozens of medeaival towns get stuck behind dozens of tractors that after you spend an hour getting out of Dublin (forget road signs, there arent any)
We had 3 days of incessant rains (locals will tell you that's normal for all the year, but I guess that explains why the country is so green.
We went mostly south and west. Kilkenny, Waterford did the beautiful drive along the coast through Ardmore.
Then Killarney and the must do drive around the Ring of Kerry. Lots of castles, Cahir and Rock of Cashel.
If you are familar with the BBC series Ballykissangel we took the train from Dublin to Avoca (Ballykissangel that was a 1/2 day train/bus tour and was well worth it.
Dublin needs about 3 full days and hase some supprisiing great restaurants (and off course pubs) DO NOT attempt to drive there unless you enjoy being lost.
If I can answer any more or specific questions drop me an e-mail.
Mike