I think the general concensus is that it's a great Symphony but highly questionable "American Symphony" that the project was supposed to create.
It's high reputation and popularity really does questioned the notion of judging the work via the intent and artistic aim of the artist as a valid concept. I really have a hard time seeing how it could have possibly succeed with it's stated goal. It doesn't sound American to me and even if I'm not an expert of American music but I generally associate it with blues note/microtonal and polyrhythms which isn't present. Even taking in consideration the fact that he is a foreigner, there have been other foreign composers who sound more American than him.
I mean listening to Debussy (a French composer who liked jazz) and even Anton Webern (a German composer who lse passacaglia sounds quite blues influence) sounds more American then Dvorak
It's a great Czech Symphony but not a great American symphony