I am not a semantic content specialist, though I consider it a very important development. I can see many advantages that will no doubt emerge in the next few years. Here is some discussion, for and against.
Lombardi's narrative structures - organizing and visualizing.
Lanier's criticism of 'single simple paradigms' - why it isn't all that.
http://www.openehr.org/mailarchives/openehr-clinical/msg01376.html - discussion on the usefulness of semantic tech in the health field. Interestingly, openehr's web site has links for Clinicians, Providers, Vendors, Government, and IT professionals but none for patients or hacker hobbyists.