Never had it as I believe we have a wonderful health system that I pay for via medicare levies. I've done the math back to front and sideways and we are better off putting the same money aside to cover things that come up. We just paid $1100 for DD to get an adjustable orthodontic plate. This will last her about 3 years and cost about the same as one year of extras at a level that covers othodontics (which then probably only pays for $500 of it).
We have ambulance cover and that has paid for itself 100 times over.