I'm still plagued with extremely poor performance panning, and zooming on large DWG files like plant layouts with equipment.  The entire application becomes lethargic and the display performance is so bad that the application is virtually unusable.  It also doesn't display all the graphics while panning until you stop panning.  As you zoom in to a smaller area, perfomance improves.  Contrast this with an Autodesk product like ACAD LT, and the same drawing performs as if it was a very small file.  I don't get it.  I've logged it with Support before, and all I got back was "it works fine here".