One of the reasons Documentum did not break through for the management of CAD files (as generated by e.g. Microstation) was that the XREF files in CAD environments used a lower level call to the Operating System (windows) to retrieve the Referenced files (CAD files are typically composed in XREF'd files). It could be kind of coped with with add-on software (e.g. McClaren has made a CAD package for Documentum, but is it not brilliant, expensive, ..)
Am I making a mistake when I assume that the CIFS support in Alfresco is probably solving this problem? If that is so, I believe that a lot of engineering departments with Microstation and Autocad become an interesting target for implementation. It is also an interesting testcase for the exploration of link support in Alfresco.