One problem we are having with sharing files between users is the unit of
measure that a drawing was created in verses the unit of measure of the system
the file is being opened in. For example if I create a drawing with some
dimensions in and I have my units set to mm's. After I get my drawing appearing
perfectly, I email it to someone and they have the default setting of inches.
When they open the file the drawing does not show what I intented since all the
dimensions are in inches.

It would be best to have the "Options" dialog have two tabs for every item:
"default" and "document". So if I set my default units to mm's then every file I
create will have units in mm's. If I send the file to my friend with her
perferred units as Miles my document still opens correctly, in her system the
defaults tab would list "Miles" and the document tab would list "mm's". 

This really should apply to many other items such as grid settings.