Horrible situation. After having Trupanion recommended by our pet's cardiologist, his clinic helped us sign up. Our dog had been covered since birth by a competitor, but this specialist, and our regular vet felt Trupanion was a superior company.
When we submitted our first two claims, they were both rejected as "preexisting conditions." One of the two was for dental work. Apparently Trupanion found that the dog had been treated for tartar, and they would not consider any future dental work.
They were happy to accept our money, but there was absolutely no rational logic demonstrated by any customer service representatives, even after appeals by the veterinarians.