I use both levels almost every time. My theory is that you might as well get twice the pop out of a load of Kingsford. The second layer is not that much extra work. And I have a lot of freezer space.
I currently have 6 racks of BB ribs on my 22 inches right now. 3 on the top, 3 on the bottom. I could have easily put them in a rack on the top shelf, but I like to cook them horizontally when possible. I have a close friend whose wife's mother is in hospice now. I told him I was bringing over ribs, potato salad, blueberry cobbler and homemade ice cream this afternoon.