I got a chance to hear a burnt copy of this, and I agree that it's very good. The first movement keeps a heavy, "trudge-y" feeling throughout the ongoing A-minor march sections, just as it should do. Yet, the two inner movements don't die. In the scherzo, Wigglesworth is very "contrasty" through the various trio sections; infusing the proceedings with lots of sudden accelerandos and ritardandos (much like Rattle). The finale is also expertly paced, and I like the fact that W. takes the final A-minor outburst at the very end of symphony, quite slowly.
I only have one beef and, quite frankly, it's a big one: the cowbells and deep bells are too distant and TOO soft. Near the start of the loud, climactic passage in the Andante movement (towards the end of the movement), the cowbells are pretty much inaudible. At that spot, they're onstage - the only spot in the entire symphony where they're placed onstage - and they're marked fortissimo. They should cut right through the loud, unison horns there.
I also can't hear the deep bells at all when they make their final appearance in the symphony. Those deep bells come in just before the last appearance of the offstage cowbells - the soft passage before the final, allegro "charge" section (in othe words, it's during the soft section located after the second hammer-stroke). Otherwise, this is a very good Mahler 6, especially in regards to tempi and tempo relationships.