A new product was released yesterday for something I used to do before I came to Autodesk and that is P&ID drawings. Expect more information very soon as it begins to make its way out the Autodesk doors after customer beta testing.
http://www.autodesk.com/autocadpid
A couple other bloggers have been mentioned the new product as well.
Jimmy Bergmark: AutoCAD P&ID 2007
John Herrman: New Autodesk Product: AutoCAD P&ID 2007
Also keep an eye on Ursala's P&ID blog, In the Pipes.