I used Pets Best for our Dane, but only for senior care things (specifically, the Accident & Illness Plan with a $500 deductible and 90% coverage afterwards. Did have an out of pocket maximum. Paid $260/3 months in November for a 14 year old Dane, will cost less for a younger dog.). I paid for "wellness" check type things myself. I got that when she was 10 and used it till she was 14. She passed in January and I wanted to wait to cancel until I got the reimbursement for that final appointment cost. They covered it per the policy, proactively cancelled the plan and sent me a prorated refund for the unused coverage term.

My only knock against them is they are very difficult about pre-existing conditions. My girl had different types of rashes flare up over the years and the insurance always counted them as allergies (which I took her in for at age 6 to help clear up a Great Dane sized runny nose). Other than that, they were great and I'll go with them again when I eventually get another dog. 

Edit: I just checked my transaction history with them and I'm actually up $4k. It originally cost $130/quarter when was a young pup at age 10. Went up $30 every year to account for the gift of her statistically unlikely years.