We called him late one night because our old heater finally died. He came as quickly as he possibly could, spent the next full day replacing our unit and going beyond to make sure everything related to it was working properly. I would recommend Mark to anyone and plan to use no one else myself. Bravo! In this day and age it's so wonderful to find someone who really cares and wants to do a good job.
Pros: Prompt response, diligence, follow through