Kenneth Woods responded to my "pseudo-rebuttal." Read it here if you want the whole thing.
The quote below really does sum up my issue, if it is that much of an issue, with Mr. Woods' argument:
Certainly studying scpres is what makes conductors better at what we do, but studying the scores of one of the great conductors is doubly illuminating. Established conductors will often loan their own copy of a given work to a younger colleague-studying another conductor’s analysis and markings is very helpful. Studying Mahler’s music not only can make a conductor a better musician, it makes you a better conductor, because you’re not just learning the symphony by Mahler the composer, you’re looking at the performing notes of Mahler the conductor. I’m not assigning papal infalibility to Mahler or Ravel, there’s always a harmonic or a bowing in any score that doesn’t work as notated. It’s not that they knew everything that could be known about the orchestra, just that they knew more than anyone else.
Maybe I'm wrong, but I don't see Mahler's scores as general advice. His symphonies are far too unique and too idiosyncratic to yield many helpful hints across the spectrum. Mahler was assuredly a great conductor, perhaps the greatest of his generation, but knowing what I do about Mahler, I doubt he'd conduct Wagner or Beethoven the same way he'd conduct his own 6th or 8th.
I would agree that Mahler's scores and revisions are tools for understanding Mahler, but so is any contemporary account (e.g., "Remembering Mahler"). My point is that one should exercise extreme caution before taking too much general knowledge away from Mahler's work. There is far too much Mahler in Mahler to find him a co-equal partner or benevolent teacher. If you've done that, and reckoned with Mahler, then go for it.