Thanks, tsuwm. Any illustrations of usage? For instance:

Man, that's a dope song! (or)

Man, that song's the dope!

I had some black musician friends who used "joint" like that, going back to the late 70's...man, that's the joint! But it was always "the joint", and it always ended the sentence...joint never stood alone in that context as an adjective (joint tune, for example). And I think that expression caught on in a large way for awhile in the late 80s or so.