I've started it recently, and it definitely helps you think through the process of how to get to a certain sound. You don't need to know anything about synthesis going into, so it does start pretty slow. I can't speak to the later half of it in regards to how advanced it gets though.

It seems like if nothing else it would be a good resource to refresh your memory on the fundamentals every so often. Thanks for sharing!

I finished the free demo and it went over all stuff I already knew, but at the same time by the time i was done with that I was able to discern differences in sounds I was trying to recreate much better than I did before. I would say that there's probably nothing in it that you could not learn with enough youtube tutorials and experimentation (that's pretty much what everyone des), but this provides the benefit that any dedicated schooling on a particular subject gives: A guided methodology of learning with built-in reinforcement of concepts that all build upon previous foundations. It's repetitive and often seems boring, so if you're autodidactic and just experiment you'll learn the same stuff eventually - the difference is something like Syntorial or a synthesizer course at one of the music production schools (point blank, ICON, etc) helps to ensure there are no gaps in your knowledge, and overall just streamlines the time it takes to gain experience. It's no substitute for experience, however!

I'm probably gonna buy it because I learn best in structured, syllabus-driven learning environments. A hundred thirty bucks is a lot for something that isn't obligatory, however, so I couldn't recommend it for someone who is comfortable just listening to SeamlessR videos all day.