I currently have an annual policy with Allianz which, in my case, has worked out less expensive than taking insurance for every overseas trip. In my case I do it mainly for medical coverage should I require it overseas.

Before this I have also used Travel Guard and made several successful claims - they are however expensive. I got refunded for the cost of rerouting and an extra hotel when the airport burnt down in Nairobi, and for car rental when a flight, after multiple cancellations ended up in Boston instead of LGA. On another occasion I received a full refund for non recoverable costs for a flight /trip I had to cancel. Although it took a while for this particular refund I did eventually receive it.

The most important is, regardless of insurance company, to keep all your records and make sure you have multiple duplicates before submitting a claim.