Well, utilization is generally low.
This comment makes some estimates:
The first month or so is the hardest, because your node gets vetted, which means tested for reliability. Only around 5% of all traffic goes to all nodes that are in the vetting phase.
But even after your node has been vetted, the amount of space used depends either on the amount of test traffic Storj Labs creates or on the amount of traffic real customers create.
Both currently is not that much. We are still missing some big customer with high demand of storage capacity.