Absolutely love it!
Only issues I can see is finding a good way to mount plate/pcb.
One option would be fixing threaded inserts in the mold, wich will become enclosed in concrete when pouring the case.
Another option to consider would be cutting plates with an concrete anchoring/reinforcing frame around the actual plate.
This way the hole plate could be enclosed in concrete when pouring, creating a single piece case/plate combo.
The case would have to be open on the bottom, but this would make for a very solid case as the plate is locked into place and even adds reinforcement to the case.
really loving the raw concrete look and shape of the case and will be closely watching where this is going!