I have heard of them but have not experienced them.  They are recommended in a couple of my guide books.  You might try a Google search using the words: Over the Top Tours reviews.  I find that works if I plug in a specific hotel name + "reviews".

unfortunately google doesn't turn up any reviews. they are linked to by several official sites, like Dublin tourism site. but no one seems to know anything about them. also, they don't seem to answer their email.

well, we shall see. I really like the looks of the tour, and would like to take it.

I did decide to book their "Celtic Experience" tour. We are going to do this as an alternative to the Mary Gibbons tour of Newgrange. We decided that claustrophobia and size were going to keep at least me, and possibly my husband, out of the passage tomb at Newgrange. It seemed a shame to go on that tour if we couldn't go in. The Over The Top tour goes to a few more places. And it visits Fourknocks instead of Newgrange. I still might not be able to go into the tomb, but we will see. And my mom, the anthropologist, decided she liked the idea of an unrestored tomb better than the restored one at Newgrange.

I think it will be a nice day no matter what, as we will visi Mellifont and Monasterboice, the hills of Tara and Slane, as well as Fourknocks. I will definitely report back about how it went.