Lisa and I booked a Princess cruise back in the fall of 2010 and we were glad that we took out the cruise insurance. When her father went into hospice we cancelled the trip and the insurance reimbursed us even for our 'non-refundable' airline tickets.
$300 worth of insurance netted us over $1,000 in savings.
If you're unsure of your situation then I'd say get the insurance.

Oh, and we got the insurance through Princess. I imagine your cruise line offers something similar, just ask.