I've had the opposite experience.  I've had Coach Net, first as a complimentary subscription and then over the past 15 years I've renewed several times.  Some years I don't need them, other years I've used them for phone advice AND towing a few times a year, INCLUDING Alaska and they never failed me and I've never had to pay for a tow.  The advice has always been from someone who KNOWS about diesel coaches.  With Good Sam's I've had friends who have had lousy service and terrible phone help.  so I guess it might be directly related to WHO you get on the phone.