I looked into it a while back, but elected against it. If you read the fine print, battery replacement is only available when the battery dips below half power: "service coverage is available for battery depletion of 50 percent or more from original specification." Not sure how Apple measures this, also not sure how picky they are about it. I bet it's pretty easy to get replaced. However, after heavy use for 20 months, my iPhone 3GS battery is still definitely above 50 percent, so I would be nervous about getting stuck with a prick at the Genius Bar. I'm sure other forums discuss the battery issue in more-depth. Just something to think about before dropping the money down, especially if you're not adverse to contract extensions and discount phone upgrades to keep up with the Jobs'