Not bad, it sums up the history of Extreme Metal pretty well. Begins with First Wave of Black Metal, then Grindcore, Deathmetal and Black Metal. There wasn't anything about the Gothenburg sound and I was looking forward to watching that. Gaahl's does not make another appearance and Sam and Necrobutcher (of Mayhem) patch things up (after their episode in A Headbanger's Journey). There are interviews with Tom Warrior (of Hellhammer, Celtic Frost and Triptykon), Alex Webster (of Cannibal Corpse), Mantas (of Venom), Dani Filth (of Cradle Of Filth), Necrobutcher (of Mayhem), Ihsahn (of Emperor), as well as guys from Carcass, Napalm Death, Dimmu Borgir, Enslaved, etc.
Despite this being a pretty good concise history of extreme metal, I still think it would have been better if there were separate episodes for Black Metal and Death Metal, etc. The whole thing seemed rushed in order to incorporate all the genres together. But then again, there are plenty of documentaries on youtube in case you want to learn about any genre in depth.