Also bought supplemental medical insurance through Insure My Trip for DH who is on Medicare. His Medicare supplemental Plan F pays up to $50K lifetime out of the country and this would pay anything after that (hopefully).
That $50K lifetime limit was a concern for me, too, as someone with a Supplement. I also use InsureMyTrip.com. "Travel insurance" can have so many moving parts (I know, I just peer-reviewed an American Academy of Actuaries White Paper on the subject). To me, trip cancellation and lost or delayed baggage are minimal risks (I fly Business Class on the long hauls and most are fully refundable). The things I look for:
1. Large PRIMARY health insurance coverage. That means Medicare and the Supplement aren't likely to pay at all because this coverage pays first- so you don't need to worry about the $50K limit. It also means you don't have to go through the trouble of running the claims through your regular carrier first. Really convenient if you're in a foreign country where they want assurance you can pay immediately.
2. Med-evac coverage, preferably to the BEST hospital, not just the nearest.
3. Some sort of referral network so you have an in-country number to call for assistance. (I've seen this sold separately at a very low cost- it's because they don't pay anything, they just help you get medical attention.)
4. Additional costs of you and a traveling companion having to stay longer, rebook flights, etc.
5. Additional costs of going home if you're, say, in a cast, need to be accompanied by a nurse, need 2 Business Class seats, etc.
6. Worst case- repatriation of remains. Keep in mind that some countries prohibit cremation, so now you're talking about the cost of embalming and shipping a body.
I'm fortunate- healthy and active, no pre-existing conditions. Last week, though, I climbed Arthurs Seat in Edinburgh (elevation about 1/2 mile) 3 days out of the 4 I was there because I loved it so much. I've gone snorkeling in 42-degree water, walked on glaciers, descended into a dormant volcano- I really want to be protected in case Stuff Happens.