I've been a DAN member and have had their insurace for nearly 6 years now. I upgraded to their Master plan a few years ago as I'm now diving beyond the recreational limits. I've had to use the insruance once about 2 years ago and I thank God I had it. I spent several hours in the ER waiting to see the Doc, several more hours in a private room waiting for the chamber ride to begin and then 5 1/2 hours in the chamber. Total cost was somewhere near $10,000 US and DAN paid every dime of it.
Thankfully, the Doc said that if it were a hit at all it was a very minor one and after the ride in the chamber I felt fine and have not had any problems since.
IMO, DAN Insurance is a must have. I won't dive without it.