Hello,
I would like to suggest a feature which I believe would be really handy. I have purchased some points (a subscription) and have used Substance Source for getting some of the materials for my project.
One thing that I missed is the ability to inspect the material a bit more. Right now the only thing we can see is some screenshots, but I think it would be handy to see all the possible parameters and maybe even the ability to try to apply this material onto the object, just to test it out, before making a final decision to either purchase it or not.