Good question. Dublin is worth 2 days,but park the car and use the tourist double decker bus,take the full tour and hop on/off after that all day to visit tourist locations.The Book of Kells in Trinity Uni,and Kilmainham Gaol are great to visit,as is the free National Art Gallery and the free National Museum.I am not a fan of the Guinness Hop Store as I view it like Homer Simpson going to Duff World.Outside Dublin Newgrange is a great visit if you like history.Across the border Belfast is a must to visit,do the Black Cab tours of Belfats darker recent history,it is sadly very interesting.Also visit the Folk and Transport museum at Cultra just outside Belfast.Back down south Donegal,the innishowen peninsula drive is great on a good day,Mayo and Galway coast roads fantastic.Kerry is great,and despite tourism Killarney is a great location and hire a bike.Into Cork the city is OKish,go and stay in Kinsale as its great for food and fun in the evenings.West Cork is great for driving around,and by and large all people in Ireland are welcoming to tourists.Enjoy,and I hope you get the weather that has yet to arrive and give us a summer,we've been waiting since 2005 or thereabouts .