As a social systems developer, I am a huge fan of relationship properties, since they reveal the meaning in relationships, and much more information is available to work with in analytics.
I have tried to workaround this in Fibery using an entity type with endpoints A and B and automation buttons, but it is cumbersome and does not really work well in practice.
I think that the idea of relationship properties is very well aligned with the character and value of Fibery and will bring Fibery to the next level of interconnectivity and analysis of data.