I've seen a couple of them and they're great. I have a few on DVD and a few on DivX. There's also a few out on YouTube.
I have:
The Who -Who's Next
Deep Purple - Machine Head
Iron Maiden - The Number Of The Beast
Judas Priest - British Steel
Metallica - The Black Album
Motörhead - Ace Of Spades
Pink Floyd - The Dark Side Of The Moon
Queen - A Night At The Opera
U2 - The Joshua Tree
Cream - Disraeli Gears
Jimi Hendrix - Electric Ladyland
John Lennon - Plastic Ono Band
Meatloaf -Bat Out Of Hell
Steely Dan - Aja
Really informative stuff if you're interested in a certain band or album. There's video clips, live stuff, and interviews with band members, producers, and staff members. Highly recommended.