With our home warranty (First American) we've found that even stuff that is covered costs us quite a bit out of pocket. For example:
Our AC went out last summer. The warranty contractor came out and told us that the part itself and repair were covered but it would be $1100 for various non-covered items due to the way our AC was installed . (Uh huh). Took over a a week to get the parts in and fix. We looked into just doing it ourselves but it would have cost more than $1100 for parts and labor, however, but we felt like it was crap that we had to pay over a grand for them to fix (not replace) a covered item.
Same deal when one of our water heaters went out - the actual heater itself was under manufacturers warranty, so we assumed that the home warranty would cover the labor. But no, the contractor quoted us over $300 to drain the old heater, and do a bunch of other crap. We talked to a local plumber who fixed the entire heater for $150, and offered a personal guarantee on the labor. Didn't bother with the warranty once we got his quote.
Disposal died, and they installed a new (crappy) one for free, but charged us $165 to upgrade the electrical portion because the previous disposal was hard-wired and the new one had to be plugged in to an outlet.
Basically, each company has their own ways to make money on the warranty work and I have no idea how many were legitimate and how many may have been exaggerated or not necessary (like the water heater labor that was obviously padded). And nothing took less than a week to fix including the AC.
Our warranty was included when we bought our house last year - we are definitely not renewing it. It just doesn't cover enough of the repair cost to make it worthwhile and the contractors they send out are not that impressive.