Love it or hate it, the main reason for the release is for historical reasons. The performance, and especially Bernstein's pre-performance remarks, caused a huge controversy in the press, and the story has been relayed ever since.
This recoding, and the excellent liner notes, correct a lot of misconceptions: Gould was in favor of Bernstein's remarks; Gould's interpretation is no longer considered exceptionally slow by today's standards (meaning the Gould must have had some effect on a few of today's artists). It is fascinating to hear what all the commotion was about.
The most interesting part is that the critics fared the worst in the judgement of time: the critic from the New York Times absolutely seems ridiculous (in his review that was written in the form of a letter to an imaginary friend!) with his snide remarks that come off as a cranky senior citizen criticizing the youngsters on the stage. And the fact that so many other newspapers picked up the story as if it was a boxing match.
Reagrdless of recording quality (originally meant to be a mono radio broadcast), this is a fascinating performance that documents a very interesting concert in the history of an American conductor and orchesetra, and deserves this wide release. It shouldn't be the only recording of this Brahms concerto you should have, but it should sit right next to it.