I think I know how to explain Jensen's voice/accent/speech here. It's "cleaner" or "clearer" than what I"m used to hearing. He's done a good job, I think, of neutralizing his accent in SPN, but I think I get now what you're saying about the "flavor" or "texture" of his speech. Maybe I don't think of it so much as an "accent" as just a part of Dean's characters.

Anyway . . . I'm really looking forward to this movie. We'll have to discuss this further when we've seen the whole film, yeah?