For the last few years, we have had the home heating plan that includes an annual maintenance as well as service calls in case of furnace failure. So far so good with the annual maintenance, and until recently no service calls were required.
A couple of months ago, we moved to a new-to-us (but very old) home with an old furnace, and we continued the plan at the new address. We didn't know whether the furnace would work or not - appliances were included "as-is."
When the first really cold day came along a few weeks ago, we had a "no-heat" situation. Called up Reliance, and they had someone there the next day, who was able to determine the source of the problem (a malfunctioning venting fan) and adjust it for temporary function until a new part came in about a week later. Second tech came in, installed the part, and did the annual check up and maintenance, taking the time to show me what he was doing (I'm interested to learn how things work) and also giving me information about some interesting new home heating solutions (also in response to my questions).
Furnace works fine now, and we're quite happy.
The only thing I would change about the Reliance experience is the scheduling window for the appointment. I think it should maybe be a 2-hour window rather than a 4-hour window, so you don't have to take a huge chunk out of your day to wait around. If that were changed, i would increase the rating to 10 stars.