I had to put my 1.5 year old tiger cat, Julio, down a year or so ago. The diagnostics alone were several thousand dollars, and there was no guarantee that whatever they found would be treatable. I had to make the call to let him go quietly by the vet's hand. I knew it was the right decision, but I wanted to make sure that my new kitten would have a little bit of a safety net. I didn't want to have to potentially make a life and death decision based on money.
Recently, my new kitten got sick with a bacterial infection (Toxoplasmosis) and nearly died herself. We got her treated and paid, confident that we would at least be receiving some reimbursement. What we got back wasn't everything, but the insurance has already paid for itself twice over. I think that as long as your expectations are in the right place, you will get a good return on your investment.
I would recommend getting your pet insured.