The whole point of insurance is to have that comfort to know that in an emergency, you know you are covered (minus your deductible).
Our dog ate something that really messed her up in the worst way. 24hrs of witholding food was still resulting in her vomiting water. So we took her to the emergency vet (since it was evening). She was very dehydrated and exhausted but ok, they sent her on her way and we thought, good thing we have insurance!
Well, we submitted the claim within two days after her visit 2-6-12, and it took until 03-21-12 to finally get to our claim and let us know the coverage of our dog. A really long time for us to have to shell out our own money and wait, but in the end they came through.