I dont know what all the GC coverage offers, but I can speak to the Daddy's Junky Music Expanded Benefits... which I assume is similar...
The Bottom line is this: if you're a person who can 1) do most minor repairs yourself, 2) have the time / patience / skill / cash to source and install OEM replacements for parts / pieces that commonly need repair on the gear you buy.... these programs are generally not for you..... much in the way that, if you're a guy who knows how to change your own oil, rotate your own tires, replace belts and hoses etc... you wouldn't buy an extended warranty on a used car.
However, these things are not true for the vast majority of people. For the most part, no matter where you go, instrument repair is usually $40 / hour for labor, and usually $75 / hour for electronics. If you're buying a solidbody electric guitar for $250, it may not make sense to buy an extended warranty.... however, if you're buying a Martin Acoustic for $1,700.00 ..... paying $60 to guard against things like bridge lifting, busted nuts, rotational twist in the neck etc.... is probably a really good idea.... since even the smallest possible thing that could go wrong will cost you well more than that to repair or replace...
my $0.02