The Malcolm in the Middle box set uses branching for the commentary tracks. For example, if you select the commentary option on the first disc, it plays the whole of the Pilot (which has a commentary track for its entire duration), and then about half an hour of clips from the rest of the episodes. Is this the first time branching has been used in this way? In my experience it's more usual for a disc with a patchy commentary to simply revert back to the film mix while the subject isn't speaking, or the viewer has to endure long periods of silence. This new technique is much better, although it does leave you feeling vaguely disorientated, as the disc hops from episode to episode!