Ireland by Rail

Yes. I did a three week trip with a bus/rail pass several years ago. There are problems associated with this type of travel, though. You have to plan carefully to make the most of your time. The type of pass I was using allows a certain number of days travel within a certain time frame, three days travel out of nine, for example, so you have to make maximum use of your ticket on the day you travel. So, from Killarney I took the train to Cork, then the bus to Kinsale on the same day. To see the Rock of Cashel and on to Kilkenny was quite complicated and involved taking the bus back to Cork, then a bus (or two?) get to Cashel. From Cashel to Kilkenny I took a bus to the train, then train to Kilkenny, all on the same day. I found the bus schedule wasn't great to some smaller towns I wanted to get to (Dingle, for instance) so I ended up staying in larger places and doing guided day trips. I had wanted to fly into Shannon and out of Belfast, but found that getting from Shannon to Killarney was also quite difficult and time-consuming by public transit. This does not appear to have changed as a google search brought up lots of forum discussions about it. If you are thinking of using Shannon I think I would fly into Shannon and out of Dublin or Belfast as I wouldn't want to be trying to get to Shannon airport by public transit on the day I was flying home. It's really going to depend on what you want to see. You may want to use the train to get to the next town, then rent a car for a few days once you get there, or just do guided day trips. Email me if you like, and I can tell you how I did it. Also, check the Lonely Planet web site, their forums will have a lot more people with experience travelling by bus/train.

Just curious, but which rental car companies have you considered? We've used Hertz several times for one-way drops between Dublin and either Galway or Shannon have never paid a drop fee within the Republic.
It does get a bit expensive if you do a one-way international drop...between Dublin and Belfast for example.

Is it the drop off fees that are so onerous, or the insurance? My wife and I traveled to Ireland a year ago, and we found that the insurance was what drove the cost up a lot. We ended up paying $700 for a ten day rental, but only around $70 was the drop fee. Either way, it's expensive to drive in Ireland. (Definitely get the super CDW if you drive in Ireland though). You could have a perfectly fine trip to Ireland relying on buses and trains, emphasis on buses. The bus network is very good. On our 2016 trip we took the bus from Shannon airport to Galway, then back again a couple of days later to pick up the rental car, and it worked great. I also took the bus from Cork to Kinsale on a stay over on business trip in summer 2010, worked great though the morning bus was little over subscribed. A good strategy might be minimizing days with the rental car and picking up/dropping off in the same location. What is the itinerary that you have in mind, if transportation were not an issue?