John: CT doesn't much seem to like Haitink (at least in recent vintage), and I can certainly understand why even if I think they're too hard on him. Karajan's famous recording, as with most of his work, doesn't do as much for me as it seems to do for millions of others. I admire the control enormously, but too often I fail to see the point of it. I haven't heard either Mehta, but temperamentally he strikes me as fantastic for the piece.
Matthew: The passage isn't just harmonically straight out of M6 but the orchestration is too. Absolutely agreed about the Mahlerian qualities. Alex Ross, not the biggest Mahler fan himself, writes beautifully in The Rest Is Noise about its Mahlerian feel. I always had anidea for an orchestral concert to put the completed Adagio from M10 on the first half and then the Alpensimphonie on the second.