I am still debating the extended warranties myself, but one viewpoint I have considered recently is this:
If X warranty costs $1200 let's say. Realize then, that basically the warranteur is in this for a profit, so they are essentially saying "On average, you will spend less than $1200 in this warranty period.". Let's just guesstimate $800, taking $400 out for their profit, salaries, building, paperwork, all that.
So basically, they're saying on average you will cost them $800 in your warranty period. Can you afford $800 when it comes time to repair your vehicle? If you can afford $1200 for the warranty, you can afford the $800 "average" repair bill then.
Now of course, like all insurance, the point is to even out the "spikes". You likely won't have $800 in Sport Trac trouble. You'll have probably $0, or $3,000. The average spike is probably in the $2000-4000 range. Is that tolerable? Obviously home insurance is a great deal because no one can usually afford the $200,000 spike of a burned down house. But "repair insurance" which is all a warranty is, the spike is much smaller. If you can eat that spike if you happen to be one of the small % that get hit with a "my tranny fell apart at 37,000", then don't get the warranty and statistically you'll more than likely come out ahead.