Sorry, I had some sarcasm in the original post, it was not meant to offend/attack anyone, only give some debate/personal experiences back to support the purchase of the warranty. I also did reference that for ME it did not seem like a service that would work or have a good ROI, that didn't mean it was a poor choice for everyone.
Personally, I have had terrible experiences with any type of warranty (original or extended), so yes I do want to read the contract and not trust good faith. Claims are either denied or refurbished components used that cause a high loss of use of the product and significant amounts of my time to facilitate the repair.
The fact that all the warranties don't offer any option for rental car coverage, towing or loss of use over 7 years/70K miles also indicates to me that the "loss" factor of the use of the vehicle becomes significant after this age/mileage. That also is a problem for me, as I live alone and have no other form of transportation, so having to rent a car that is not included in the contract will become increasingly expensive as the years progress, making the ROI (again for me) not as practical as for other people. Everyone should be figuring in the costs of having the vehicle towed in for repair as this is a cost.
"Repairs required as a result of other than a manufacturing defect (such as a design defect or normal wear)" This is under the Not Covered section and yes this is separate contract from the manufacturer. But if the service contract I am purchasing references manufacturer specifications (as it does for maintenance responsibilities for the owner) then what the manufacturer has stated is important in court. If the vehicle is designed for 150K miles, under normal wear, any failure after that mileage would be caused by normal wear, not a manufacturing defect (any failure prior to that mileage would be a manufacturing defect of the part). If I was on a jury I would support that all failures after 150K miles can be denied coverage. No different than the owner supplying maintenance records that match my owners manual to prove the car was adequately maintained. Additionally, design defects are not covered, so problems like the shudder if it gets worst could be denied (even if it makes the vehicle difficult/annoying to drive). Now, this is where the company is going to have their actuaries look at the cost to cover such a claim or the cost to deny it and take the hit to reputation.
In my opinion, the contract has a lot of exclusions and language that protects the service provider more than protects the purchaser.
All other items aside, the simple ROI for each individual is going to be different as everyone's situation is different. For example, I would pay cash for the plan today versus investing the money in the stock market (long term ROI is around 8-11% over 30 years), would have to include the cost of renting a car and include the loss of my time. Loss of my time is calculated very high in the ROI calculation since focusing on my career has exponential value when you factor in the time value of money (getting a 7% raise this year versus 5% is really important as every raise after that is compounded growth). Since dealing with car repairs is worse than having to go to work, I would rather spend that time at work. Other people may find the lost hours to dealing with the warranty provide a better payback as the cost of the savings is larger than the revenue they can garner.