Here's the Gramophone review of the original set on vinyl. I recommend seeking out the individual symphonies' reviews as they provide greater detail on performance and recording. They can all be found (relatively) easily using the site's search engine.
Jonathan Swain made a brief reference to the recording of the 6th during the BaL review. He was not over-enthusiastic about the tempi adopted. I got the set to replace my damaged LPs. I might try to rescue a few of the 'fill-ups' form the vinyl, however. Sorry, but I don't recall having read any reviews of the set at the time I bought it in LP format. I simply got it on trust, and was happy with what I heard.