Yes I do, always have done and yes I have called upon it on more than one occasion. My two are insured for (can't remember the correct terms) veterinary fees up to $5,000 p.a. plus cost of euthanasia & disposal of body. Only exclusions are pre-existing conditions.
In my experience, if your horses are worked hard, in potentially challenging conditions, then insurance is worth it because accidents do happen to horses!
However, I have friends who own gobsmackingly expensive dressage nags who don't insure because the cost of the premium is a large fortune.
Now I'm in Canada, I'm with Capri.
Get up, get going, seize the day. Enjoy the sunshine, the rain, cloudy days, snowstorms, and thunder. Getting on your horse is always worth the effort.