I've seen all six of them, found especially the ones with Cullotta and Calabrese jr. interesting. Ron Previte annoys the shit out of me, but even he gives some interesting insights. The episodes are short though, and some of them not that interesting.

Cullotta gives an interesting back story to Spilotro's 'Hole in the Wall' gang. Calabrese junior's relationship with his father really was a sick, sick situation. Senior was / is a real psychopath.