I was in a van on what the Irish consider a "highway" (i.e. 1.5 lanes winding through the mountains with an inch of snow on the ground) and I thought it was really cool - but then, I have a deathwish when it comes to driving, so unless you're like me and enjoy precarious roads all while getting used to being on the wrong side, the Paddywagon tour might be the way to go.
I've heard a few people knock Paddywagon and say that Shamrocker tours are cooler, so you might want to look into them, too.
As for what U2 said - I saw cars getting booted & towed in Dublin constantly. And my boss has tons of tow-away stories from Cork, so yeah, be careful