A much better translation than that of Rossi (aka Japrisot). The Saumont translation is much more informal. Saumont uses the passé composé instead of the passé simple, which, of course, places the narrative in a much more conversational register. Saumont also makes masterful syntactic and lexical choices to render in French the slangy, teenage male register of the narrator.
Of course, I'm making these comments from the point of view of a native speaker of American English who was 14 when _The Catcher in the Rye_ was published, so I am much more familiar with how the English "sounds" to an American ear than how the French translation "sounds" to a French ear. The English sounds very natural, very much the way a rebellious teenage boy of that era would speak. I can only guess how natural the French translation sounds, except that my French is good enough, I think, to recognize that the Saumont translation is more faithful than Rossi's to the conversational, slangy register of the original English.
I would be very interested in hearing the opinion of a native French speaker.