Believe it or not, it depends. I had 9 rental properties in addition to a stressful full-time career where I traveled around the United States. My biggest problem is that I did not have time to run every single problem to conclusion. So, what I did was make systems and processes to allow myself the capability of 'stepping back' from repairs at my rentals.
Expensive: Yes. But zero frustration. I don't want to know my tenants comings and goings. Nor do I care. I don't want to be at the property when the dishwasher (for example) is being fixed. I put a LOT of responsibilities on my tenants. :-)
Cover 'everything': Not only no, but hell no. You need to look at these policies as 'first steps' to getting things fixed and make sure that the items YOU want covered are in the policy. Most will NOT, for example, cover roofs.
If you have an air conditioner in Arizona blow up in the summertime (like I have), you need to have a Plan B, C and probably D. ;-)
Warranty Companies 'Suck': Yup, some do. Some are more responsive than others. The thing to remember is that these companies, although sometimes national, work differently in different parts of the country. SOMETIMES differently in the same METRO area! As I said earlier, we have 9 rentals in 2 different Metros in 5 different cities. And we use 3 different warranty companies. Confusing? Can be, but that is why God made Excel. ;-)
In essence you are trading money for time and peace of mind. That doesn't mean you STILL won't have problems, just hopefully fewer.
With that said, I would not own a property WITHOUT a home warranty.
My $.02
AG