Abbado's previous recording of the Sixth (from Chicago) was decent but unmemorable. This one is a disaster.
First off, he uses Mahler's revision of the work, which places the scherzo third instead of second. Nobody knows why Mahler made the change - most speculation is that he was afraid of what the nasty critics of his time would say about how similar the openings of the first movement and the scherzo were - but it's hard to deny that the change makes narrative and tonal hash out of the piece. Let's see: we start in A minor and end in A major with all problems seemingly solved (or at least at bay), then we go off to the other end of the tonal world into E flat for introspection and nostalgia (because we're unhappy and need healing because of those solved problems?) then we go back to square one for the A minor scherzo and, when that winds up to a cry of horror and winds down to a whimper, we go back to the other end of the tonal world to start the nightmare finale in C minor (a hemisphere away from A minor but right next to the E flat major that the slow movement ends in). Right.
Second, the performance is bland to the point of wimpiness. There is no edge that Abbado doesn't bevel into smoothness, no harshness that he doesn't underplay or coat with plush. The epic struggles of the first movement are reduced to genteel conversation, the deep mysticism of the pastoral interludes becomes background music for pleasant chatter. The triumph at the end of the movement is subdued because there isn't much to triumph over. The slow movement sounds more lost than normal in second place because Abbado mutes its pain and aching nostalgia. The scherzo sounds almost jaunty, not demented or sinister. The finale works up some steam about 2/3 of the way through, but by then it's hard to care. The ending, which can be devastating in other hands, is matter of fact here.
If you want to be scorched by this symphony, try to find the Mitropoulos Cologne recording, most recently out on the now-vanished (thanks EMI!) Great Conductors of the 20th Century series. More available alternatives include Tennstedt, Karajan, Bernstein (Vienna, not the wretchedly played and crude NY), Dohnanyi, the slow but intense Barbirolli Philharmonia, and the poorly recorded but fiery Neumann Leipzig (not his Czech Phil remake). But almost any recording would be an improvement over this sorry issue.