Extended Warranties are a HIGHLY PERSONAL decision, based on your financial situation, tolerance for risk and type of rig you own.
If you own a DP, a major engine or transmission failure COULD cost you over $10,000 in repairs. An AquaHot replacement unit is $8,000 - $10,000. A fridge replacement is $1200 - $1500, much less than the other items mentioned, but not insignificant either.
IMHO, the decision comes down to:
If you suffer a major failure will your rig sit dead in your driveway while you continue to make loan payments, but cannot afford the repair?
or...
What is your tolerance for risking the situation above?
If you can live with either of those, don't get an EW. If either of those would eat at you constantly, seriously consider an EW, if for nothing else but peace of mind.
If you decide to buy in...... RESEARCH is paramount! This is one situation where reading and understanding the "fine print" mandatory. you need to be 100% certain you understand what is and what is not covered. Remember the cost is always negotiable. Since your rig is new, you'll probably be able to negotiate a better deal, but be 100% sure that the EW term kicks in AFTER the manufacturer warranty expires.
Lastly, prepare yourself for the reality that you will probably never recoup the premium paid in claims made. Obviously, as others have said, that's how the warranty companies make their money (and they make lots of it). Look at an EW as an insurance policy, because that's exactly what it is.....
When we bought our 2003 Executive in 2011, we did a 2 year EW (XtraRide Platinum). Expensive but excellent coverage and service. We didn't come close to recouping the cost (alternator was the only repair), but those two years gave us peace of mind while we got to know our coach.
We decided not to renew, but MIGHT look into a policy that covers the drivetrain only, just to cover a major catastrophy. We'll see......