On average it ain't worth it...since it is sold to make a profit! Question is...are you feeling lucky or above average?
Seriously... I've been investigating them myself and found some major differences between what policies cover and exclude...so it is more of an individualized question than..."Are extended service contracts worth it?" Just as an example...I was offered a policy by my dealer that was $2k less than my GoodSam quote...but when I went home and analyzed what would and would not be covered...I still felt the Good Sam was the better value.
That said...what I cannot get past is that none of them seem to cover the actual structure of the motorhome at all...no roof, no sides, no floor, no frame. This after they try to scare you with talk of a motorhome being a house that goes through the equivilent of hurricane force winds and earthquakes and needs to be covered!! Except the house ain't covered!!
So...my decision at present is to pass on all of them. If anyone knows of a policy that DOES cover the house... please pass it on. In the meantime...I'll just go with the Ford chassis warranty and the various component warranties and hope the odds remain in my favor. If I were buying a used coach, I'd probably go for one.