Overall, estended warranties tend to average 90% profit for the company and 10% return for repairs. While that average might not apply to your specific purchase, it is something to always keep in mind.
Generally, the only time it pays off is if you buy something that is cutting edge (unknown reliablity), expensive (something you can't replace without a major problem to your budget), and likely to break (some items are quite simple and have few things that can possibly break).