John was excellent. He: (1) serviced the furnace; (2) advised us about a gas line that was installed over the unit which is not recommended; and (3) identified the source of a problem we were having with the furnace blowing hot air once a day, interfering with air condiditoning. He is coming back to give us quotes on installing a gas line to our balcony for the BBQ, and some options for increasing the effectiveness of our system this winter, likely through the installation of a reserve tank. John is efficient, friendly, knowledgable, and thorough. I wouldn't hesitate to recommend him to anyone.