I agree with both Harleysrock (who says buy the insurance) and LTSteve (who says don't). For years I used my credit card insurance with no problems because I never wrecked the car. Then another DR1'er cautioned me about this method. Think about rolling into the airport with only two hours before your flight is about to leave, and your rental car is bent in half, totally destroyed. Do you think you can just hand them the keys and tell them that your credit card company will take care of everything next week after you get back to the US? Most likely they will not let you leave the country unless you swipe a $20,000 charge on your credit card to buy them a new Chevy Aveo, and then YOU can fix everything next week with your credit card company and hope they honor their credit card car rental agreement. Also, you may be swiping a 70,000 SUV on your card as well if the accident is your fault, so you better have a high credit limit.
The insurance is somewhat of a scam, and expensive, but to me the extra $100 is worth it so I can enjoy the trip a little more knowing that I am covered. (hopefully)