If you purchase the new Autodesk DWF Composer to markup DWF files and more you will also get a DWG file viewer. It is based on AutoCAD. In addition to viewing, you can also Publish files to printers and DWF files and even use page setups and plot syles. The DWG viewer is a seprate application from the Autodesk DWF Composer.

Thanks to Brian Roepke of the Autodesk Inventor Team for pointing out that you also get this DWG Viewer from the Vault CD for Autodesk Mechanical products such as Autodesk Inventor Series and Professional that include the Vault CD.

Opening a DWG

Viewing a DWG

Plotting a DWG

Publishing a DWG to printers or DWF

You can also manipulate the layers

You cannot use the command line however as this is a very limited viewer for vieing, plotting, and publishing.

Cheers,
-Shaan