Haven't been in myself and I would agree with the "dodgy looking from outside" comments, but we have friends who swear the Royal Oak in Kilmainham is a very welcoming, comfy spot - with open fire and friendly dog if I remember their account correctly.
Dare I raise the question of what folks think of the oldest Dublin pub (ok, inn if you want to get pedantic), the Brazen Head? Despite it being our closest pub, we don't go in from year to year, can't handle the coachloads sipping glasses of Guinness with "hmmm, different" looks on their faces.
Cheers, bighair