The Dynamic Sphere (DS) is a fantastic catalog of techniques. Having personally acquired almost every Aikido book on the market, no other book to date contains that variety of techniques (except maybe Saito's Takemusu series). When I first started Aikido I bought DS. Each time I bought another book after that, I was disappointed at the tiny subset of techniques that were demonstrated (almost always ikkyo-gokyo, and irmi-nage, kokyu-nage, kaiten-nage, tenchi-nage and koshi-nage) because I knew there were more!
That being said, there virtually no technical tips accompanying the techniques. Other books explain the finer points and nuances of the techniques, while DS just shows you how the technique is done.
It is a fantastic resource for beginners through to intermediate because they can see the variety of techniques offered in Aikido -- something they are not likely to see in a year's worth of training in our standard dojos (at the rate of 2-3 classes a week).
But you will need to get more technical manuals, videos and simply question your sensei in order to understand what makes each of those techniques work (especially against varying conditions such as uke resisting, or uke is much taller than you, etc.).
The text does sort of read a bit like stereo instructions, but being a technical-minded person I enjoyed that approach. It tries to address all the factors of Aikido in a very scientific manner -- not cluttered by esoteric double-talk. And while this is good for the beginner to intermediate, the advanced student will often wish to understand things like Ki, zanshin, etc. which require more philosophical approaches.
So all in all, DS is the perfect intermediate book. Some beginners might like those little 30 page primers available, and advanced students would prefer texts that address technical issues (for example "Total Aikido" from Gozo Shioda).
And the problem with DVDs is the medium doesn't suite portability. You can take a book anywhere, and flip to page 100 in a second and be practicing -- try that with DVD.
When those mediums have been made more user-friendly then they will start to replace the paper-mediums -- but that's a long way a away.