i was there a few weeks ago, and drove 1,300 miles, 2,100K's, over a week, and we had a great time, i guess the longest drive was the first day, after the red eye from EWR to BFS, i didn't sleep, and did a 5hr trek from Belfast to Dromoland Castle down south, had a BMW 5 series with just 600 miles on it, from Hertz for just 224 GBP's so that eased the pain. Relying on the credit card insurance, the total cost in USD was c $400.

Driving around Ireland has changed a lot, from the last time i did it, the small roads, to the now toll ways, a completely different experience.

Have fun.