Can't comment to that company, but statistically you must be better off without the warranty or they wouldn't sell it. There is also the risk of them going out of business which I hear a lot. If you roll the warranty into financing you will find you will pay 10,000 or so for a 5,000 policy.
Now, having said that I have zero experience with one, and for some people it could be a great thing. This is my first MH so no telling if I regret it, but I still think all above still applies.