I love commentary-tracks, but I mainly stick to director and writer-tracks. Cast-tracks rarely interest me as much. The original Clerks-track is a classic, but I was a bit disappointed with the new one. It sounded like the well of information was really starting to run dry.
Favourite contributors are Soderbergh, Terry Gilliam, Ridley Scott, Oliver Stone......... and probably a few more I'm forgetting at the moment
Must admit that the commentary-tracks by Arnold I've heard (Conan and T3) are among the funniest I've ever heard. Unintentionally funny that is. Hearing Arnold explaining the reason why you get the scene with the T3 enlarging her breasts is comedic gold.