It use to be, specifically in Acad 2009, that I could use the "Paste to original coordinates " function much more than I can now in 2012.
I would select objects, copy [to the clipboard], go to the destination file, paste to original coordinates.
These days, that option is grayed out more often than not. Maybe something changed that I am not aware of that is making this not possible.
BTW, I am NOT going to/from drawings that have had the corrdinates rotated or altered in any way.