Kiwi has Embrace Pet Insurance and they have been great! I chose them because they covered hereditary problems and Kiwi has recently had liver issues. If she had another insurance, they would not have covered all her blood tests, trips to the vet, and a nuclear medicine scan!
She had her nuclear medicine scan on the 20th and I got an email from them today saying they were sending the check out today! And they are soooooo nice! The lady that has been handling my claims sent me an email asking how Kiwi was feeling! You can completely customize your policy either with high or low deductible, high or low copay, etc. So you can control how much of a premium you want to pay.
As far as having to pay in advance, I think every pet insurance company works that way. It is kind of a bummer, but I did talk to a claims person at Embrace and they said that if someone has a signifigant vet bill, they sometimes will work with the vet's office so that you don't have to pay everything up front. But you can think of it this way, it is better to have the insurance because maybe you could borrow the money to pay the vet and when you get the money from the insurance company, you could pay the money back. It would ensure that you wouldn't go bankrupt trying to save your baby.
P.S. I forgot to add that Embrace doesn't offer preventative coverage. They believe that a pet parent can save for those expenses. They are more for accident/illness coverage.