AutoCAD Layers to ArcGIS Feature Classes
The ArcGIS for AutoCAD AutoLISP routine (ESRI_LayerToFC) is a short cut to defining GIS features from your existing drawings. It will make feature classes for each layer containing possible GIS features. If your drawings are primarily organized by Layers this might be a helpful tool to make short work of defining your feature classes in ArcGIS for AutoCAD.
Try typing (ESRI_LayerToFC) at the command prompt of AutoCAD with ArcGIS for AutoCAD loaded and see it work. It is an unsupported sample routine, but it seems useful to me.