So what are your thoughts now that you've played with the demo?
For me, I'm getting it, but I have a need to produce large material libraries for my videos and I can't expect the students to pay for textures to be able to learn -- it's very confining for me to be constrained to the available free textures because I really can't teach some of the things I'd like to.
Here's a marketplace for substances made in the Substance Designer application:
http://www.turbosquid.com/Substance
The thing to remember here is each substance can be varied to thousands of material variations with a few moves of a slider... once you've built the substance it becomes a "on the fly" texture generator for you (and I mean texture in the Maxwell "texture/normal/displacement maps" sense).
This is particularly useful in game and film texture design.
By the way those of you who use 3D Studio Max 2011 here are some videos about how the materials work in your program:
http://www.youtube.com/watch?v=W7OArcBmyFM
http://www.youtube.com/watch?v=3kGtBIFrWkw
Best,
Jason.