Autodesk Inventor

[#1]

As I said,

...vanilla AutoCAD 2012 will import a whole host of CAD filetypes.

[#2]

If we really want to go back into history vanilla AutoCAD used to have free IGES and STEP translators but these were removed somewhere around v2000 or 2000i from vanilla.

They were still available in AutoCAD Mechanical and MDT.

Added back in vanilla 2012, along with a whole bunch of others.

http://blogs.rand.com/manufacturing/2011/03/autocad-2012-product-announcement-new-features.html

http://static.ziftsolutions.com/files/8a7c9fef2eb74447012ec97702324a77.pdf

[#3]

Perhaps it requires install of free Inventor Fusion (which is automatically part of the AutoCAD 2012 install) as indicated on this website, but I don't think even that is really correct.

I think that only gives you the option to go directly from AutoCAD to Fusion for editing, I don't really think it is required to get access to the translators.  But even if it is - Fusion is free and promoted as being pretty much a companion to AutoCAD.

http://autodesk.cadgeekspeak.com/2011/05/i-can-import-what-with-autocad-2012/