First time I drank a full drink was a pint of Guinness. I felt sick to my stomach just sipping it. I kept ordering it and it kept getting better and better.
The fist time I had it though it was the most aweful thing ever. I learned later that after sampling a few different pubs that it can make all the difference though.
Watch where you buy it from
Edit: in addition, the question I have is why do people say its so "thick" ? I mean, to me, a milkshake is thick. It isn't even anything like regular (2%) milk. I don't know. I'd say its about as thick as skim milk? but nothing more