I ran into a group of Irish gents whilst walking around last night, 3 from Cork, 1 from Dublin. I have this tendency to do accents from many countries, but especially from various parts of England, Scotland and Ireland. I held off for a bit, but couldn't help it....
I started with the easiest one, the Cork dialect (basically sounds like the typical drunken irishman, very heavily accented and gregarious). Both the Corks and Dubliner said I was dead on, so I didn't feel bad when I kept slipping into it; it's hard for me to be around accents and not want to practice.
The Dublin accent is seemedly easier, since it is much more subtle; but that subtlety is where the complexity lies. I had to actually think about that one, but when I did it also worked.
It was also quite intriguing to see the class difference they spoke of, between Cork and Dublin. Dublin the "higher class" and Cork the "working class". They definitely had some tensions.... but the crazy American speaking in each dialect kept their humors up!