We used this tour as a way to see all the main attractions around Dublin (and I'm not going to lie - also as a way of getting around the city!) My partner and I were in Dublin for four days and did the tour for the first two days. We got our ticket through our hotel, 16 Euros per person for two days. It is a really good way of visting all the major attractions, especially the ones that are a little out the way of Central Dublin. Being hop on hop off, we did a whole circuit to start with and then went back on over the next two days to visit the attractions. However, as I mentioned, it is also a great way to travel around the city generally and is also a good way to familiarise yourself with Dublin. After the two days, we knew our way around the city and made our own way around for the days after. The drivers on the live tours are really informative and bring the commentary to life in a, enjoyable and funny way. The recorded tours take a more traditional approach. I would certainly recommend doing both if you have the time (this is not to say the drivers on the live tours are not informative, they are! It's just good to get two perspectives). We also got a leaflet with a small discount to some of the attractions and restaurants.
Overall - very worthwhile, enjoyable and good value for money tour. Pick up the leaflet with money saving coupons!!!