I just visited the AutoDesk website to find that they are now pushing users towards the DWF format rather than using PDF for delivering drawings to clients.
From my experience clients want a no-nonsense solution to viewing and printing drawings. They want to open the drawings with a viewer they already have and are comfortable with rather than download ANOTHER viewer just to open my drawings. Some users have a hard time with the whole zoom/pan concept, especially when you embed the DWF in a frame on a web page.
AutoDesk, if you're listening, lets get some cutting edge solutions (like 3D Studio Max for instance) and quick playing games to gain market share. Also, please fix your DWF viewer to work with two monitors correctly.