I've been using a Johns Brothers Heating plan for the last 6 years and have been very pleased with their service. Last winter, my 25 year old furnace had "issues" in December, and they were there promptly to help me out. The cost of the work and items replaced were more than the cost of my service plans over 4 years. This year, I decided to put my A/C system on their care plan as well, and have so far been pleased. They also have an oil prepurchase plan for the year that I think is a great deal.
PROS: great service and options
CONS:
more