I use this rack to hose an X32 Rack version with extension, two drawers for Berhinger PM16s and as a recent addition, three wireles IEM transmitters.
Rack rails on the back allowed me to rout all connectors I need exposed to panel mounted sockets for easy access.
The rack rails on top allowed me to mound devices whos connectors I didn't want to manuially route to a rack panel, like the Behringer ultranet extension, and a midi interface, and usb hub.
While it has gotten quite crowded in the rack, everything fits perfectly, making the heart of our band compact and easy to transport.
With rack mouned devices coneccting and stabilizing both side walls, the rack is stable even without the lids mounted. With the lids mounted you can stack other heavy stuff upon it without issue.
As we have two smaller racks without wheels, we use this rack as transportation platform ofer flat surfaces. The wheels are absolutly necessary if you fill a rack of this sice to capacity.