Initiated to prevent the piracy of the Mahler symphony poll thread-
O.K.: My thoughts- 1) I respect the conductors, including many of the very greatest, who have omitted this from their repertoire. 2) I recognize that there are no small number of people who view the dissemination of this work as a kind of sacrilege. Having said that, to accuse Deryck Cooke of "charlatanism" is a little harsh. Let's give the accused the opportunity to speak in his own defense: "[I'm presenting a] performing edition, [upon which Mahler, had he lived] would have elaborated, refined, and perfected, in a thousand details, and finally, of course, embodied the result in his own incomparable orchestration." Cooke went to extensive pains to explain that he was crafting a "performing edition" and not a "completion." I think this attitude is also not alien to Remo Mazzetti, who figures in the other prominent edition of this work. Admittedly, it's an imperfect view of a Mahlerian world, but it is a view nonetheless, which, I think, has its merits over an opaque covering permanently hiding those famous final sketches.
So (flicking glove to ground), I say "treasure." Glad I've heard it, glad I own recordings of it.