I never travel without it but I don't it from disney. I have some coverage with my existing insurance and it's easy to add on for a lower cost to get more comprehensive coverage for a trip. I also know there is some coverage available from some credit cards (amex mainly but may not be limited to that) so you might want to inquire there as well.
You really need to reach each policy but there is a lot of things you could claim from travel delays, fees if you didnt' get a 100% refund if you had to cancel (for certain reasons), medical coverage. If something serious happens generally there is some type of coverage and help but again read the policies and decide if you want to have that coverage. You just never know what's going to happen and it's nice to have coverage if something does.
I met a couple families one trip (back when I didnt' get it). One was on a dream florida vacation for 2 months (yes 2 months at disney), they were from canada. They got food poisoning and dehydrated and had to leave after 2 weeks because they couldn't afford to stay after the 1 night in the hospital health care costs they just got. They even said if they had insurance we could afford to stay. Same trip, someone else that I met who knew this family as well said it doens't matter about international. Someone they knew that was older fell and had some injuries from the fall. They had health coverage and the costs they incurred is somethign they may never pay off because their coverage wasn't the same when traveling.
You just don't know what's going to happen when your traveling.