We did the tour six years ago and have mixed feelings about it. At the two pubs we visited we were ushered to a private room where the leaders took turns talking and performing. Unfortunately for us, it was Culture Night in Dublin and things were very crowded, so other pubs on the tour had to be eliminated--therefore it wasn't much of a crawl. The leaders were quite entertaining though and we really enjoyed the music. It was the first "session" we experienced on our trip--we enjoyed many, more enjoyable sessions in small town pubs later on. I suspect the pub crawl would be less of a treat if you do it towards the end of your trip rather than at the beginning. If you've never attended a trad session, the pub crawl does give you some context for what you'll be experiencing on your travels.
At the end of our evening, the crawl leaders asked for volunteers from the audience to perform a song from their home country. We were lucky enough to have 10 or 12 members of a Danish choir (in town for a performance) on our tour. They did a lovely Danish folk song in amazing harmony. Unfortunately we also had a drunk American who treated us to an awful rendition of This Land is Your Land. All in all, an interesting experience--I don't regret it but I'm a little sorry we chose it over the Literary Pub Crawl.