Are you referring to medical coverage while you are away, or insurance that covers the cost of the trip is something goes wrong (natural disaster, illness that prevents you from making the trip, etc.)?
If it is the former, check with your medical insurance to see if you are already covered. My dad had a stroke on a tennis court in Mexico, and it cost him nothing because his regular insurance covered everything, including a medical plane flight back to the States. If you aren't covered, then it is probably smart to purchase something, but I'd go for a no-frills plan.
If it is the latter, I think that in most cases, it is a waste of money. Most airlines in most places will put you up if you miss a connection. (I spent a night at the Radison in London just last week, thanks to British Airways.) If you have a complicated itinerary with lots of connections made of different reservations, then it starts to be worth considering, because RyanAir doesn't care that you missed your flight because British Airways had a delay, or because your train to London arrived late. But it it is a fairly simple trip with one set of round trip tickets and a hotel, to me, the insurance is a rip off.