We're thinking about buying the PremiumCARE ESP for our Energi. However, we're going to wait until 35 months or 35,500 miles and then decide, based on if we expect to actually keep the car through the end of the extended warranty period. I studied Risk Management in college so I have a thorough understanding of how insurance works, and this is essentially insurance. But, sometimes the peace of mind is nice to have even though you expect to lose money. There's also the Risk Aversion factor. The more risk averse you are the higher the value placed on the peace of mind offered by insurance.
I think we'd also end up using it for a bunch of little things rather than big things, that's why I'd pick the PremiumCARE which effectively extends the bumper-to-bumper warranty with a $0 deductible. The hybrid components are covered 8 yrs/100k miles so they wouldn't be effected by a PremiumCARE ESP, the powertrain is covered 5/60 so its extension by the ESP wouldn't be that great. Plus, with an Energi vehicle the ICE is hardly used so it isn't likely to have problems.
I shopped around on the inter web and found Flood Ford out of Rhode Island has the best price and the cost of the plan begins to increase after 12 months or 12,000 miles. One thing you can do is go to their web site and price out the cost based on mileage and months of ownership, you can input and numbers you want and it will give you the cost.