Having watched the whole documentary, I feel there are a couple of points that are worthing noting for potential buyers - neither of which should put you off, though.
First, the disc is in 4:3 format - fine if you have a square telly, but on a widescreen telly with the top and bottom chopped a bit (to avoid black bars left and right) the captions for interviewees are chopped a bit.
Second, some of the videos for the songs are of poor quality. I know this is old film from the 70s but surely there are better prints available?
OK, so whinges out of the way, on to the good stuff. This is an excellent documentary. The first hour or so sets the scene, with the historical setting and also the way German musicians (and youth) handled the post-war years. This is followed by the beginnings of electronic music (not just in Germany, although there is that bias) with interviews with a lot of the early musicians (Klaus Schulze and Conrad Schnitzler amongst others) as well as various music journalists and technical staff. All good stuff, but if you're waiting for the Kraftwerk bit then it is a bit tedious.
Finally we get to Kraftwerk and the context of their music, working through all the albums from Tone Float to Computer World (almost no Electric Cafe - pity - and a very small mention of Tour De France Soundtracks) with contributions from Karl Bartos and Rusty Egan, amongst others. This concentrates on the earlier albums - up to and including The Man Machine - in great detail and is informative, if a little long.
The opinions from the interviewees are interesting and varied, and in the Extras there is a little (5 min) feature about Dusseldorf vs Berlin electronic music, as well as an extended interview with Karl Bartos.
So, to sum up, a good disc, although the documentary is a little long at 3 hours. Good job there are plenty of chapters, so you can remember where you got to instead of having to start again! I'm glad I bought and watched it, and if you have an interest in Kraftwerk and/or German electronic music then it's well worth considering.