I have Trupanion, but haven't made a claim yet. I also have some money put aside for Cinders, and a credit card to use just for her. All I can tell you is that once you decide to get insurance, enroll. The younger you get the puppy signed up, the better.
That way, if something happens, they won't consider it "pre existing". Pet insurances won't cover an illness if your pet was treated for it before getting insured. Mine will cover hereditary things, that's why I picked it.