I saw it in the theater. I'm not the biggest Metallica fan (but worship the old stuff like all), and it was good. Really good. Ironically enough, I already was a fan of the flim makers. They made a couple other documentaries which were fantastic; Paradise Lost (about the West Memphis 3 murders), and Brothers Keeper (about a murder 'mystery' in upstate New York). I dug the shit out of both, back when they came out, and Metallica provided the soundtrack for Paradise Lost, incidentally. The teens who are accused of the murders are big Metallica fans, and the music in the background is just plain eerie when they show the murder scene and stuff (it's in rural Arkansas). Plus, they use only odd passages like stuff from Orion, it's stunning.
Anyway, when I heard it was these guys who had made the movie, I ran right out and saw it. If you can be a bit objective about it.....just forget your feelings on Metallica, it's a VERY interesting view into the life of a big ass rockband....that is falling apart. Warts and all it certainly is. And from a purely "interesting" point, regardless of the music you like, I think you all might get a kick out if it. It's a REAL documentary, for what it's worth.
The release promises lots of extras, though I will rent instead of buy.