I watched all 4 DVDs over the course of a couple weeks last Spring. Before watching them, if you asked me about the myriad of software synths I own, I'd have said "I don't really understand most of what they do, and they're all totally different". Now, not only do I understand the individual instruments much better, but - crucially - I can see how it all fits together, and how they all basically follow the same pattern, whether it's a slavishly reproduced Arturia vintage synth, or the latest of Rob's incredibly line of instruments (hell Blue II)!
Added bonus, not only is the material incredibly comprehensive and great at reinforcing its principals the more you watch, but the book itself is a retro work of art in and of itself.
If you need/want to understand how synths - real or virtual - work, and how to make them work for you, there can be no better investment than this book & DVD combo.
A perfect combination, then, of form and function - like everything else this company makes.