After suffering through shoddy repairs from home warranty companies for years, we found Howard Air's maintenance contract. It's been awesome! They come out twice a year to service the heating/AC unit and keep it running. Before them, we'd have breakdowns every summer (and have to wait days for service in 100+ degree heat). Now we have a company that will send someone out almost immediately if we have a major problem. But the best news is - since we've started using them, we've only had a problem once (and they covered the labor since they had just serviced it)! Preventative maintenance works!
Even though our unit is old, they don't pressure us to buy a new one or do major upgrades. They clearly explain any issues and provide options, not requirements, for repairs. My only complaint is that they used to do hot water heater emptying on the plan, but it looks like they moved that feature to a more expensive package. As long as they keep the AC running in the summer, we can handle the hot water heater ourselves!