It's been a year since the last comment on this guy, but he's one of my favorite actors, and so I must pay my respect. I echo the sentiments of the first poster, Timberwulf. Duvall plays all his parts convincingly by becoming the character. He's turned in many fine performances, and he's one of the few stars that I'll always give the benefit of the doubt to, meaning that I might suspect that a movie he's in may not be very good, but I'll give it a shot simply because he's in it.
Oh, and you know he had to have SOME talent; he hasn't been around for getting damn near 50 years on his looks alone, right?