I would really think it is dependent on the actual animal. If you keep some of the breeds of dogs or cats that tend to have health problems, allot of the types of bulldogs for example, I would think it to be a good idea. I guess it really depends on the cost of the insurance and what is actually covered/copays. It couldn't hurt, I see some things on TV or the net, And wonder if I would be able to afford some of the surgeries/procedures I've seen on some animals.
I am actually looking into insuring all of my animals. It will partly be mortality insurance, and partly medical, as it is in the best interest of the company to provide easy medical care. There are a limited number of legitimate places to acquire this though. I will probably get something figured out in the next year.