I guess it would depend on the vehicle and how long you plan to have it.
Alot of people change vehicles every 3-4 years. With new car bumper to bumper warranties being within that range, it might be a moot point.
Laterly there seems to be a bit of a trend towards people buying used cars that are 2-3 years old. With that, you may want to consider an extended warranty. Depending on the mileage on the vehicle when you buy it, you could possibly get protection to take you to the 3-4 year point where you trade it off again.
I guess the thing to remember about extended warranties is that they usually come with a deductable amount that you would have to pay regardless. But by that time, anything that goes wrong with thew vehicle would cost considerably more to fix than the deductable amount, so the choice would be up to you.
eg: a smaller FWD car... the CV joints go out on you... $1000 - $1400 to repair... do the math, you could pay full pop yourself or just pay $200 and still get the problem fixed.
Alot of the times, the problems may be minor, so you may be able to band a few minor issues together, and just pay the deductable amount and get it all fixed at the same time.
That's my take on your question KYG. Hope it holds bearing for you.