I agree with Tracie that I've not found any that are "great". I've had American Home Shield on one of our houses and Best Home Warranty Company (BHWC) on another and I HATED American Home Shield. There are websites that are dedicated to people who HATE American Home Shield for the stunts they pull when it comes to getting them to pay for a covered repair.
I've read that they send out repairmen from companies their parent company owns who are trained to find something wrong so that they warranty company doesn't have to pay. Now, I don't know this for a fact, but that's some of the stuff I've read on the Internet.
As for our personal experience with them, we have a house that was built in 1992. In 2004 I believe, we had a problem with our A/C and had them come out to repair it. They said they would NOT pay to repair it, and in fact, would no longer cover our heating and air conditioning system because the technician they sent said it was "improperly installed". He said it would cost something like $1500 to fix the issue with the installation. We paid for another licensed repair person to come out and make the repairs and asked him if the system was "improperly installed" and he said no. It was installed properly. He explained what the problem was and I believe it cost about $400 to repair. Needless to say, we dropped American Home Shield as soon as the plan expired.
Now, we've had much better response from Best Home Warranty Company with regards to getting things fixed, but there are still some things that go wrong. It seems that they don't own repair companies in our area like American Home Shield does so they use smaller repair shops and don't pay them very much. Those contractors are the ones that can cause you headaches in some cases. For instance, they sent out a plumber to fix a leak in the guest bath in our rent house. That contractor said the problem, once again, was improper installation and that it would cost $600 to repair. The house, and that toilet, had been there since 1985. That was 21 years of "improper installation" that just happened to start leaking. After the warranty company said they would not cover it because it was improperly installed, the plumber happened to call me and say they would fix it for less if we wanted them to fix it. $200 less. I called the warranty company and told them what the plumbers did. I told them I wanted a second opinion because my husband works with a lot of plumbers and he said it looked like it just needed a new flange or something like that. The warranty company said they would send out another plumber, but if that plumber agreed with the first, we would be charged another $50 service call. I said ok because I knew the first plumber was crooked. Sure enough, the second plumber came out, replaced a little 50 cent part and we didn't have to pay another service call fee.
Another time, there was a problem with the heater. The first repair guy said the coil was dirty due to improper maintenance so the repair was not covered. We paid another repair man to go out and clean the coil and make the repair. They said the coil wasn't dirty and that time it cost us $400 to get the heater repaired. We didn't have much choice since we had a renter and it was below freezing and we needed to get them some heat. But if that contractor that they sent out to make the repair had been honest and just fixed it, it wouldn't have cost us $450. The problem is the contractor would have probably only gotten $50 or $100 to fix the same thing they normally get $400 to fix. That's why they do that. At least that's my theory.
It's stories like that that make you hate warranty companies. But if I had to recommend one of the 2 I've had first hand knowledge of, it would definitely be BHWC, NOT American Home Shield. The one thing you need to know about BHWC is that they ONLY write contracts in Texas at the time of the home purchase. If you own your home already, they will not issue a warranty in Texas. You can renew once you have the warranty, but you can not buy a new warranty unless the home sale is occurring at the same time so you'd want to let your realtor know that's the company you want to go with at the time of the sale.
Good luck! And please let us know if you find a warranty company that is actually good! I think that would be a rare find. :-)