Revit Structure (v1.0) has just been added as a 30 day trial download from the following link:
Revit Structure is a new release of software based on the Revit platform that is designed for engineering and documentation software. This allows you do have bi-directional linking to analysis software and link to architectural models (both ADT and Revit Building) while using the parametric change management of Revit.
If you are using a third party structural analysis design program (ETABS, RISA-3D and ROBOT Millennium are currently supported with more coming) your model will stay linked and any analysis changes that need to occur will automatically update your model which are then updated throughout your project views and construction documents.
Another large item (eluded to above) includes the ability to use 3D object based model files created within Architectural Desktop and will export as 3D structural native objects back to Architectural Desktop after analysis. For any objects that are not supported within ADT (structural walls, etc...) will come into ADT as a mass element. With the ability to export structural elements, you can also send this file to Autodesk Building Systems for interference checking between ducts, pipes and structural members. If you are using Revit Building you can continue to use the interference check for any possible issues (Tools>>Interference Check).
Of course for those working with others on vanilla AutoCAD you can still import or link DWG files directly as either reference geometry or as a starting point for your design. Revit Structure supports importing and exporting DWG, DWF and DXF format files that will allow you work easily with most cad packages on the market.