John Rodriguez, a new co-worker of mine, pointed out that it is now VERY necessary to notice what the INSUNITS value is set to for any drawing that you wish to INSERT or XREF. This only mattered in previous version if you dragged-and-dropped via the DesignCenter.
If INSUNITS does not match what the current (destination) drawing is set to, a scale factor will be applied. This has left some users baffled as to why their drawings with the same base and coordinate location do not land in the same area when inserted or xref'ed.
The INSBASE value and the factor that will be applied now appear in the INSERT and XREF dialog boxes in the lower right hand corner. Be aware of what they report.
The change can be explained with a quick look into how INSUNITS is defined in HELP.
In 2005 it said:
INSUNITS - Specifies a drawing-units value for automatic scaling of blocks or images dragged from DesignCenter and inserted into a drawing.
In 2006 it says:
INSUNITS - Specifies a drawing-units value for automatic scaling of blocks, images, or xrefs inserted or attached to a drawing.