Just got back from Dublin!
If you are going to use the hop on/ hop off bus tour, buy the 3 Day "Freedom pass" at the airport. It was a great value for 25 euros because it includes the transportation to the city center in addition to 3 days worth of hop on/hop off tour (which alone is 15 euros for 1 day).
Cork was a thumbs up, and so was the Blarney Castle. I'm glad I decided to go, and not listen to the nay sayers. We flew from Dublin on Ryan air and dispite the rain, and had a brilliant time. Ryan air was an excellent value, but there are hoops to follow.
PM or post if you have any questions on Dublin. I can't wait to return!!!