Mahar's is a pub. I think they have food, but it's not why you go there. Mahar's is the place to go if you like the taste of beer. They have a fantastic selection of beers from all over the world.
This is not a place to get drunk. Mahar's is actually a quiet place, and there are rules of behavior. I've never seen anyone get thrown out, but I've heard that it happens.
You can register and keep track of all the beers you've had. When you get to certain numbers, like having tried 100 different beers, you get prizes, like a mug or a t-shirt.
My favorites tend to be the Belgian flavored ales, but I always like a good Porter. The bartenders are very knowledgeable, and a good way to start is to ask them for a recommendation.
I used to go more -- when I was in law school I lived nearby. Now I go less than once a year, but I should find a way to get there more often.