Been here three times and overall enjoy my visit each time. National is located conveniently on 8th Ave. in the downtown core - but is inside the shopping centre making it a bit harder to find. (upstairs on the 3rd floor). The restaurant has a main level and a patio which was fantastic in the summer. Great beer selection, bar rail as well as a decent pub style food selection at reasonable price. Service was standard and nothing to note.
Would recommend as a joint for post work booze and dinner if you're in the downtown Calgary core.