Well, we have VPI Superior Plan for our 10 month old pup, and they have been pretty good about covering things. I have heard of people having to call them for returned claims, but they do straighten things out and mail you a check when you pursue them. There is a deductable and after the deductable they pay about 90% of the bill. They covered portions of the spay, shots, heartworm&flea medication. But other than that, I feel more comforable having the insurance because if there is an accident, and my dog breaks her leg or something, they will cover a significant amount of the bill that can run up to 2000 dollars.
Actually, tomorrow I will enroll the Chi we are getting on Friday.
I don't know about other companies, but I trust VPI more because they are the biggest pet insurance company.
You can call them and talk to them about your concerns and they will tell you what they do and don't cover.
Good luck with your search.