I've had Pets' Best for about four years, and among other miscellaneous claims have had to cruciate ligament claims. Both were honored per the disclosure, direct-deposit payments were fast, and claims were easy (and got even easier with the second injury, via simple on-line form submittable). I have not had pet insurance with another company, so I can't offer a first-hand comparison, but I also haven't wanted to go to another insurer.
For what it's worth, a coworker had originally recommended Pets' Best to me, based on his good experiences.
I wrote a brief synopsis of what led me to choosing to buy (non-company specific) pet insurance in the first place, available to view at