I have always had a great experience with hop on and off buses both in the US and Europe but this was not the case in Dublin. I made the BIG MISTAKE of turning in my voucher to the Red hop on and off bus instead of the Green hop on and off Bus. My husband and I are active mid 60's but even at that it is nice to be able to get a seat to enjoy the adventure and sites when riding on the bus. Out of the many times that we hopped on and off in 2 days, we were actually able to sit twice the entire time while others were standing in the aisle everywhere. This is on top off having to stand in lines and not actually get on the bus because it was standing room only while we watched the Green buses and Yellow buses both hop on and off stop multiple times in front of us with seats available. It seems their answer on when will there be another bus is 5 minutes when actually we waited 20-45 minutes at the stops. Since this was our way of getting around to see the city the two days we were there, it was very irritating and not acceptable. So my advice - CHOOSE THE GREEN HOP ON HOP OFF BUS AND DO NOT GIVE YOUR VOUCHER TO THE RED HOP ON AND OFF. Inquire with Viator if your voucher is for any hop on off or just one color. Once the driver takes your voucher, you can not use the other buses like in cities such as Edinburgh where we found the hop on and off wonderful but I did use only Green although I could have interchanged. I hate giving one star but in this case, it is deserved.
The hop-on hop-off bus in Dublin was excellent. Even though traffic was congested, it seemed to keep moving pretty quickly and we never had to wait long to get back on. We were always able to find a spot on the top of the bus and it went to all the places we wanted to see.
A little difficult to find the tour office but we did after asking several people. Be sure and bring ear buds if you want to hear any of the commentary as it is very loud and hard to hear if you are on the top bus deck.