Though you may hear this comment about many places in Pittsburgh, D's Sixpax & Dogz is a bit of an institution.
This place used to be a tiny closet-like neighbour bar. It has expanded in the past couple years, moved the beer around and now they keep most bottles in a walk in beer cooler. They also have a rotating selection of draft beers. They still have a beer cave in the back.
The beer selection is quite good. The service can be both good and bad, depending on the server you get. The place is very relaxed. The food isn't particularly memorable. I enjoy the fish sandwih. Fries are good. It's great for groups. It can get quite busy.