I could be wrong but I think BOS-PIT service has been increasing recently. For a while they were down to 2 non-stops a day on Sundays. They are back up to 5 now. I also think they are running more 170's and less CRJs on weekdays. Still no non-stops on Saturday though...
ETA: Saturdays BOS-PIT non-stop seems to make a reappearance starting in June with 2 non-stops a day.