The documentary is also on Blue Underground's Run Man Run DVD and one of KOCH DVDs but don't remember which. The KOCH version is not remastered while the Blue Underground one is.
Some nice behind-the-scenes footage and few short interviews but not much else. The way the spaghetti western genre is presented is like "look, those stupid Italians are trying to make westerns, isn't that funny!?" Also, wtf does that "John & Wayne" duo have to do with anything?
Mostly poor but you can't go completely wrong with something that features so many spaghetti regulars.
edit: the KOCH DVD is Shoot, Gringo, Shoot!