Drafter for MKM & Associates, Mark Douglas, maintains an "In the Dynamic Interface" blog which focuses on new technology for AutoCAD, DWF, Lisp, and anything cool. One of his recent postings is entitled AutoCAD 2007 -DWF Attach....Ohh YEAH!!. Check it out. Mark even shows how to import a PDF via DWF.
The DWF Attach command brings in the geometry from the DWF file on its own individual layer. Although a mish-mash of layers in the DWG and another set of layers from the DWF could get complicated, some users would like to see this. They would like to turn off portions of the attached DWF. This is something that can be considered for a future release as DWF usage evolves. After all, in addition to printing, interaction with AutoCAD is one of the ways that DWF files go beyond the paper. AutoCAD users will want to do more and more with their design data.