Here is one example for the known issue that VBA enabler slows down AutoCAD.
If you insert a block using _insert it will be quick (in our case 3-4 secs) for a larger drawing inserted. When inserted via command line without dialog box (for example: _-insert "C:/temp/ow.dwg") ist takes more then 30sec.
It happens with Map 2013 SP2, 64bit. Apparently this performance issue has been fixed and doesn't occur anymore in newer releases. Shame that it took me quite a long time to figure out, that VBA was the culprit.
Map 2013, SP2