Interoperability:

EAD’s hierarchical nature and flexibility make it a more powerful tool for archivists, but that same hierarchical nature and flexibility make interoperability harder than it would be otherwise. In other words, translating a title into EAD is not as simple as translating a title from MARC into Dublin Core is not as easy as crosswalking Marc 245 "Last of the Mohicans" to Dublin Core "Last of the Mohicans" title.

An interesting discussion of EAD conversion problems resulting for its hierarchical nature is at this blog, http://metadataintern.blogspot.com/. Go to the entry "The end is in sight. Or, is it?"

Particular angst is over OAI conversion issues.

The debate over EAD and interoperability has received some attention from the archival community. At the 2002 SAA convention Christopher J. Prom made a wittily titled "Does EAD Play Well with Other Metadata Standards: Searching and Retrieving EAD Using the OAI Protocols."

EAD crosswalk construction is not impossible, but it is complicated, by EAD’s hierarchies, wrappers, etc. In other metadata schemes crosswalks can easily be constructed between neatly analogous elements, not so in EAD.

The Library of Congress and Getty provide for the following transferal options:
(the Getty crosswalk page is at: http://www.getty.edu/research/conducting_research/standards/intrometadata/metadata_element_sets.html)

ISAD-G to EAD
EAD to ISAD-G
Dublin Core to EAD
USMARC to EAD

Notice that conversion from EAD to the other metadata schemes is not covered.

RLG (the Research Libraries Group, a non-profit university consortium) offers its own service, cooffered with a for-profit known as Apex CoVantage, for conversion to EAD:

http://www.rlg.org/en/page.php?Page_ID=448

The SAA also offers a conversion service.