The majority of our project make use of xrefs. When I drawing has multiple xrefs the layer list can become quite long and tedious to scroll through to find the layer you need. Keeping track of them inside of the layer dialog box can be frustrating. Sure you can save a variety of predefined layer states or snap shots but there's a great option in AutoCAD that makes it super easy to list the layers by xref. Click on the image at left to see.