Welcome aboard Yoann, and thank you very much for your interest in Bella!
Bella’s material system has been designed to be highly realistic and accurate while at the same time be affordable and intuitive to use. We have been very focused in their raw usage, but making them easier to use and understand is, a Jeremy said, a direction in which we are moving. Not only is a thing in the UI side, but through the use of a good documentation, sample scenes, video tutorials, and so on.
For the moment I think the IPR is helpful in the sense that it allows you to touch and see interactively, but definitely we need, and we will, to take more actions.