I like a few of their songs a lot; others, less so. On the Run, I'm Gonna Put You Down, etc. are really great but sometimes I feel like some of the beats are not quite on point and really could be better (Dirty Pickin, for example, eh). Overall, I do enjoy the music though. The use of all the bluegrass samples in making hip hop is interesting and its an approach which (while of course hip hop was borne out of sampling older music) seems pretty unusual but when it works, it is grand!
To be honest, mixing in old tunes to back emcees in rap isn't all that new.
I think the way they put it together, though, is really engaging. I think the piece you presented speaks more about their great sense of musicianship than simply innovation. And honestly, when it comes down to it, great musicianship is the real king.