Short answer: Do it!
I spent eight full days in June exploring Ireland with J. It is such a beautiful country and I could not recommend it more for all travelers.
We crammed a lot into eight days! It was enough time to get a great feel for the country but we could have easily spent more time there without running out of things to do. And, while renting a car is definitely not necessary (we didn’t), it would open up more possibilities of small towns and coastline to explore. [...]