I have had mixed results, all with American Home Shield. The warranty was in place on our home when we bought it. Our house was built in 1993 and has has it's original HVAC system (3 condensers and 3 evaporator/furnace/air handlers). The home also has a pool with it's original equipment (2 pumps and a filter). We also have a roof that's nearing the end of it's useful life (not covered by the warranty). We took an overseas assignment and began renting the house, so the system updates were put on hold and the warranty was renewed. Using the warranty I've had the following replaced/repaired without issue:
1 of our 2 water heaters replaced
A Dishwasher Replaced
An in-wall water leak repaired
Pool filter (sand) refurbished
Cracked Water Pipes (Pool) Replaced
Evaporator Coil Replaced
2 Furnaces Repaired (Make sure your filters are clean or they'll reject the claim for lack of routine maintenance).
Where they really suck for us is Air Conditioning equipment. They obviously do not want to replace a condenser so every time we get a call on one (at least twice a year), they just clean it and top off the coolant. They limit the coolant covered by the warranty and rip you off on the extra. So much so that we've stopped calling them for HVAC maintenance. We usually get the system repaired for less than half of the co-pay and coolant charge combined. If our guy ever says a unit is toast, we'll then call AHS and push them to replace it. Also, they own Greenway Home Services. So, for general home repairs that's who we get, at least in Memphis. They suck. Our experience with every other contractor that works with them has been great. But Greenway sucks. Did I mention that Greenway sucks?
I really haven't done the math but I think we're hovering just below the break even point with the premiums. It's pretty much a policy we keep in place in case of multiple failures of expensive systems. We have upgrade plans in place, and when we're done, we'll cancel the policy. I can't really recommend a warranty, but I can say it's served it's purpose for the most part.