Chris Yanchar has written a nice tutorial on the interoperability between AutoCAD 2005 and Architectural Desktop 2005 on his blog "Between the Walls".

"With the new ability for AutoCAD 2005 to natively read in ADT drawings, I thought a short tutorial about the advantages of collaborating with consultants with native ADT drawings versus exploding to 2D would be helpful. Also discussed is the basic interoperability between the ADT Project Navigator and the AutoCAD Sheet Set Manager."

Link to Article: Click Here

Cheers,
-Shaan