We adopted a senior persian cat and didn't have much hope of finding an insurance willing to cover him. The ASPCA accepted him luckily, and we assumed the coverage would be minimal at best. What we got was comprehensive coverage that was better than any of the insurances our other (much younger) pets have.
A few months ago, Remington stopped eating and it took a battery of tests to find out he had kidney disease. Once that was detected, the maintenance was costly (liquid medicines, sub-q fluids, etc). In one of my claims to the ASPCA, I attached a letter and requested special consideration because I lived in NYC and the general costs were higher. They responded by covering the cost even more. I can't tell you what a relief that was. Unfortunately Remington was diagnosed with cancer last week, and it comforts me to know that cost is not what has to be first and foremost on my mind.
Pet insurance really is great. There were a few times when I thought Remington might be sick or was behaving weird, and knowing that I had pet insurance was the deciding factor in taking him to the vet, and I was always glad I did. It was such a comfort to have a competent insurance company as a safety net.
ASPCA also has great customer service; I like that I can call and actually talk to a friendly human being right off the bat. I don't feel like a number.
If you're on the fence about insurance, do it. I'm so glad I did and I wholeheartedly recommend ASPCA.