It's really big back there. It holds an enormous volume of stuff.
4x8 sheets of plywood fit inside with the doors closed, and so do 10-foot lengths of pipe.
It's easy to access stuff at the front or the back. It's all contained under a roof in a locking, conditioned space (3 zones of HVAC) and is easy to get to from either sliding door or the back tailgate.
Works great for hauling stuff like sports equipment, outdoors gear, or photography equipment. Mine is full of tools, ladders, and boxes of wire right now, but it's been awesome for taking a mountain of camping gear and a PA system across the country. (Or, you know: Groceries. It does groceries very well indeed.)
(It's not so great at hauling stuff like bulk stone or mulch, but that stuff is usually pretty cheap to get delivered.)