Thankfully the 2007 documentary Punk's Not Dead doesn't try to answer the question of what is the real punk, instead embracing the diversity and presenting the controversy from as many different angles as possible. Using interviews from over 150 members of the punk community, with representatives from every major era and approach (mostly from the UK and USA), it presents the 'punk-eye-view' of where the genre came from, what it's core tenants are, and, most interestingly and contentiously, where it is now going.
The only 'downside' I can see about this film is that because it is produced by an American team it does not see the UK 76-79 scene as the be-all and end-all of punk, though it clearly holds it and the continued UK scene in high regard. This is no back-slapping and retro focused Punk: Attitude, focusing on a brief 3 year period of creativity from one city so 'trad punks', people who picked up their haircuts from London postcards, or folks that think The Offspring and Green Day broke up their special little party may be upset.
So if you are either a dedicated punk, who just wants to enjoy the constantly entertaining views and stories of the giants of the scene being interviewed, or just an interested observer, who wants to know more about Punk as it enters middle-age I heartily recommend this for your viewing pleasure.