Back in 2002 when I purchased a 2001 Grand Cherokee Limited, I spent $800 for a 7 year 100,000 mile extended warranty going against the advice of many old timers in this group who recommended not purchasing extended warranties. The warranty was a Chrysler warranty. This year (May 2009) the extended warranty just ended and I have tallied up the work done with the extended warranty, which came out to a little over $1200.
The only disappointment was that the 10 disc cd "player" that failed and was factory installed and a jeep brand was not covered in the extended warranty because it was not part of the "radio unit" as it is external to the unit and as such an accessory.
But the biggest comfort, for me, in having an extended warranty is knowing if there would be a major problem you will likely be covered.