Although almost all of the professional reviewers found this a disappointing recording, I tried it because of the combination of the Staatskapelle, Sinopoli, and Mahler. The same combination in Mahler 4 is just amazing. I already had my reference recordings from Bruno Walter released by Andante and Boulez n DGG. But I was blown away by the sheer depth of this recording. Where Walter invites us to sympathize with the departing one, Boulez invites us to the transcendental , Sinopoli shows us the human condition in all its beauty and hollowness. I did listen to Haitink, Klemperer, Solti, Krips, and Bernstein performances, all which I think are still easy to find, and I can not understand why exactly this one under Sinopoli is so hard to find.
As a note: The Andante release of the LIVE performance of Ferrier, Patzak, WP, and Walter is also hard to find. But it also comes with a reference Mahler 4.