Stefan thank you for your video never know about this soft so it looks interesting.
I make quick research and find that:
1. it's mainly Boolean method so everything that can be done with this soft can be done with MOI.
2. It's like MOI do not work natively in poly modeling. It exports its result to poly model and make cage like MOI.

So the only one advantage I can see is interactively updated result of boolean.

Moi has tested in a lot of different areas from hard surface to organic stuff and precision CAD modelling and it proves his power. But what we can say about this one?

I think in first glance it looks interesting but it has to be tested to make some deeper conclusions and do not deceive yourself by only watching this videos that looks so attractive, try to work in it and make some complex project after that it will be clear. MOI has a lot instruments that I think is not implemented in Groboto. For example I can not see any way to control fillet.
Look here: http://www.youtube.com/watch?v=N3wN9MssMKg when it modeled all corners are sharp but when converts to poly they are smooth.... So it will be interesting to see how you repeat my model in Groboto with all controllable fillets it has.

I can made some mistakes do not went deep in this soft, so you can correct me anytime no problem.

And it defenetly can not be used for precision modelling.