I remember seeing Arthur Penn once around 1989 at the Telluride Film Festival; Penn and Penn & Teller were there to promote the film PENN AND TELLER GET KILLED. All three were, if memory is correct, on an outdoor panel where Arthur Penn was on the end of a brief tongue-lashing from a local Telluride woman (decidedly not a festival-goer) intent on using him as a punching bag for her disdain for Hollywood and its filmed product, which she apparently found values-deficient.
Certainly, THE MIRACLE WORKER, BONNIE AND CLYDE, THE LEFT HANDED GUN, THE CHASE, ALICE'S RESTAURANT (haven't seen it, but should ), LITTLE BIG MAN and NIGHT MOVES form the cornerstone of Penn's reputation as a film director. MICKEY ONE (Penn's first collaboration with Warren Beatty) and THE MISSOURI BREAKS (Penn's second time working with Marlon Brando--who, from his performance, had a different film in mind) are watchable, idiosyncratic misfires.
And, as Mr. Wells mentions in his HOLLYWOOD ELSEWHERE post, Penn was out of cinematic fashion by 1981. Two of his later films (TARGET and DEAD OF WINTER) were genre thriller stuff that could have been made by just about anyone.
But Penn had a good run from THE LEFT HANDED GUN through MISSOURI BREAKS and deserves posthumous attention from younger generations of film enthusiasts.