Bought it and had to use it.
We scheduled a Sea/Land trip the week of Thanksgiving 2014. It was to be a 3 night Bahamian on the Dream, and then we would finish off the week in WDW. We had this booked a year in advance and bought trip insurance. The Dream departed on a Sunday, even though we joked about it, we told my nephew to not pick the Saturday before the trip for his wedding. He did, which meant we know had to fly out the day of the cruise. We went to the wedding, left part way through the reception to get home and sleep for we had a 6am flight from PIT to MCO via AirTran (Southwest had recently acquired AirTran but they were not integrated yet). Got home and got my son to bed (7 year old at the time). Within a few hours he woke up that his stomach hurt and eventually got sick. This was due to all the cookies and sugar at the wedding, etc. We got him back to bed, and decided let's get up as planned and see how he is in the morning. Around midnight AirTran called informing us our flight had been cancelled due to maintenance. Being Thanksgiving week, it was busy, the best they could do was get us on another flight (now connecting) that would get us to MCO at 4pm. They could not transfer us to a Southwest flight, nor would any other airline have a flight that worked out. I had AirTran book us anyways so we at least had flight but had to then wait until the morning to call
DCL about options.
Longer story short, we could try to get a flight to the Bahamas on Monday and meet up with the ship (not really an option for a 3 night cruise), or cancel. DCL was great in that they canceled the cruise and filed with the insurance company who I then called right after and started the process. What I found out was the insurance would only cover us if there was an act of god or someone was sick since the airline could still technically get us to the airport. Since my son was sick the night before, they suggest I fill out the forms, have it signed by a doctor and submit the claim. Being a Sunday, we went to MedExpress and had my son checked out. They agreed it was probably just all the sugar and excitement of the day but signed the form he should not fly for 24 hours. We submitted the claim and also called WDW to see if we could get a room a few days early from our planned Wednesday arrival. We had AirTran book us flights on Monday and flew to MCO the next day without issue.
We lost out on a cruise, but still had a week at WDW. Within a few months I had the refund from the cruise. Which we turned around and booked another for later that year. For every cruise since then, we always buy the insurance, and always fly down the day before if not a few days before.