I work for a small firm and our projects at this time are small retail improvements, classroom remodels and an occasional building addition or small new construction.  We have been successfully utilizing AutoCAD 2006 with minimal use of the ADT portion of the package. It has been my advice to my firm that we continue to use 2006 instead of upgrading to 2007, 2008 and now to 2010 and using the ADT.  I have used ADT in the past and have only seen it to be useful for large projects.  I feel it would be to my firms best interest when turning to Object Modeling to begin with Revit.  Can anyone please provide me with an advocate approach as to whether or not I am guiding my firm in the best direction? 
Any help would be greatly appreciated.  Thank you.

As you are already aware that ADT has been stopped and Revit is what you get when you are under subscription. I have used a revit and it is much better than ADT . I would recommend go ahead with Revit any time. 

This also ensures that you are updating at regular intervals.
 
Tom
www.indovance.com
 

ADT ("AutoCAD Architecture") has not been stopped - in fact a new version 2010 was just released two weeks ago. So if you are happy with the AutoCAD-based environment, you can go with it.
 
Personally, I would also prefer moving to Revit - but it depends on your preferences.