My seller paid for one as part of our house purchase. I won't renew it when it expires. Its quite a racket, honestly. If you call anyone out for any reason, its $60 out of your pocket to pay the contractor. It seems that the contractor's job is to then figure out how its not covered under the insurance contract, but *since* he's already there, and you've already invested $60, he can take care of it for another $50/$100 or whatever.
I suppose maybe if your air conditioner completely dies, or something like that, it may be worth it but from my experience, I'm not impressed. How many years can you pay them $400 a year for home warranty stuff, before you could have just bought a new air conditioner?