It's definitnely worth the price, since it comes with a CD of the full performance too. I wish it was a full performance DVD instead of just CD, but the overall package and DVD was interesting. Also, in this age of peripatetic, jet-set conductors, its nice to see a conductor work so doggedly with one orchestra for so long, and achieving such wonderful results. I do think Zinman relies too much in his interpretation in the DVD interviews on the alleged biographical links with Mahler's life pushed by Alma in her later years, many of which are doubtful, and frankly of no real use or concern to anyone trying to understand the symphony on its own terms. Looking to the biography to explain the symphonies can be helpful at times, but it can also be pushed to extremes that obscure the music, and I think its usefullness is limited.
For example, take the so-called "Alma Theme" in the first movement. If he said what Alma claims he did about that part of the movement, my guess is that it was an offhand comment, perhaps meant to placate Alma after an argument or some such thing - "Oh, look Dear, I've depicted you in such lovely music!" - and that he never intended it to be some genuine interpretation of the music for others. I've always thought Mahler himself would be appalled at the thought that 100 years later people would, relying on Alma's uncorroborated testimony written decades after the fact, call this part of the first movement the "Alma Theme," and treat it as if it were simple program music, as if listeners should say, "Oh, isn't that lovely...he's set Alma to music. He must have loved her greatly," every time they hear it. I think this is one of those cases where the alleged biographical links obscure, debase, and unnecessarily limit thoughts about the music on its own terms. Again and again in the DVD, Zinman seems to come back to Alma, as if she and their relationship were the key to the symphony.