I had taken this ride over 20 years ago, and decided it was time to do it again. We took the "Bridges" tour, and it was lots of fun - and informative too. Our guide was very knowledgeable and had a lot of stories about "John D" and also about events on the island during the last century. I agree with a previous reviewer that he did tend to stray a bit into snarky comments about the inefficiency of government bureaucracy, but since his comments weren't the least bit partisan, we gave him a pass. There is nothing like riding the roads built for carriages on a carriage. It was a delightful way to spend a morning!
By the way, if you make a reservation, see if they will let you request an open carriage rather than the higher one with seats across. I've done both, and the open one allows you to interact with all of the members of your party rather than sitting in rows.