While Autodesk is hoping "everyone" uses DWF for transmitting and archiving drawings in a PDF-like manner, SolidWorks is busy at extending support for their eDrawings.
Geometric Software Solutions is writing extensions to make eDrawings work with other CAD packages. The first was Pro/Engineer. and today GSS announces the second: Wildfire (the new Pro/E).
GSS says that eDrawings for Pro/E has been adopted by more than 4,000 users in three months. (Is adopted the same as downloaded?) Is this a good number? I dunno. Presumably, the downloads/adoptions are by customers who don't use Pro/E.
The 4,000-number is made murkier by there being two eDrawings: one is free; the other, called Professional, is US$995 per year, followed by $195/year thereafter.
While it's nice to get software for free, it costs money to produce. If it's from a hobbyist, it may well stay free; if it from a corporation that seeks to stay in business, at some point free disappears. Either the company disappears, the product disappears, or users start paying.
eDrawings is initially free; the Pro version costs money. Acrobat and Distiller cost money, but are included free with Adobe software products. DWF is free right now, so expect Autodesk to start charging for some aspect of DWF use.