We use AutoCad for all our templates and prototype displays. Occasionally we have to make Omega and AutoCad "work together". I've had the best luck transferring files by sending an .EPS to Adobe Illustrator, exporting as a .DXF and then e-mailing that.
As far as receiving, though, I've never had a problem IF they save the .dxf as an OLDER AutoCad file. Sometimes (I guess it all depends on the mood that day) the files work with AC 2000, sometimes it has to go back further. We haven't updated our AutoCad software as of yet, but we have had the same problem with files sent in by clients with the newer versions.