This stainless steel bowl is part of the Smoke-EZ extension kit. It fits right inside the charcoal ring, so I can use it this way when I'm looking to add some extra moisture to the cooking environment.
My criteria for using a water pan or not in the Kettle is this: For a small quantity of meat, I use the water pan. A lot of meat in the cooker will produce enough moisture all by itself, so then I skip the added water.