If it weren't for the fact that my Partner In Cuisine and I can walk to the Union Grill whenever we want, we'd probably never go there. The food and service are pretty decent, but they aren't really anything you can't find anywhere else. Between the two of us, we have pretty much tried everything on the menu and nothing really sticks out as being superlative (except maybe the waffle fries). The old stand-bys are the fish sandwich, the French dip and the salmon salad.
During the warm weather the Union Grill offers a lovely opportunity for al fresco dining on Craig Street. Unfortunately, because of the lax smoking rules in Pittsburgh, there's always someone standing 5 feet from you smoking a cigarette. Because of that, we sadly always have to eat inside.
I do like if you order a soda, that you get it in a gigantic glass - this avoids the need for your server to keep running back and forth, refiling pop. Their alcoholic drinks are somewhat more expensive than the other bars in Oakland, so between that and the fact the place closes so damn early (I think 10 during the Summer), the PIC and I rarely go there unless we are too hungry or lazy to think of anywhere else go.