My son and his wife have it for their 3 dogs through the local Pet Smart store which has a vet clinic inside. The insurance pays for periodic checkups and immunizations, and either full or partial spaying/neutering, but I don't know what else it covers. I do know it does not cover the surgery the one dog needs to correct cherry eye (both eyes). The surgery costs $1500 and the kids don't have that kind of money, so the poor dog will eventually be blind. However, she knows the house so well and gets around so well that no one would ever know that her eyesight is as poor as it is. She still plays with the other 2 dogs and acts as normal as can be.
The amount of coverage you get probably depends on how much premium you pay, just like any other health insurance. You will just have to check it out with different vet offices and clinics. Good luck!