I don't know whether insurance works the same for you as it does over here, but I consider it essential. Like any other type of insurance it's a gamble - do you pay for it and end up not using it, or take a risk and not bother, and just hope that you don't have any vets bills you can't afford. It's certainly helped me.
I took out insurance for my 2 kittens when I got them 9 years ago. Didnt claim at all for 8 years then last year one of them died from a blood clot in his neck. Got in from work to find him lying on the floor paralysed and needing immediate treatment. He died at the vets 5 hours later and the treatment cost me just over $3000. It was going to be a lot more but he deteriorated before they could give him some new drug to disperse the blood clot (injections that were going to cost $800 per shot and he would need several). Without insurance I would have had to have him put to sleep almost immediately as I couldn't have afforded that, and would have definitely had to say no to the injections. As it was, I was able to give my consent for them to do what they could and the insurance company paid for it all minus $30 excess. I worked out I had received more from them than I'd paid in over the years. With Jaffa (now 9), the only claim I've made so far is for a dental earlier this year. That was nearly $800 though so I was glad I could claim for it.
For me it gives peace of mind and the knowledge that I can give my boys whatever veterinary treatment they need, and will only need to say no to treatment if I don't feel it's in their best interest. Money won't be an issue.