After my experience with them, I do not trust many of the reviews on here.
We had an issue with our HVAC unit freezing up. It took them 3 visits, multiple tests, and over $500 later to tell us we had low refrigerant. It is also only a few years old and has gotten significantly louder, but we have no explanation. Low refrigerant seems like an issue that should be detected on the first visit. They may seem nice, but they are a total rip off.