A February 2012 update (PDF) from the NIH states "No harm to publishers is evident" after 4 years of the Public Access Policy.
The policy mandates that NIH-funded research must be made available for free to the public. All final peer-reviewed manuscripts, arising from NIH funds awarded after October 1, 2007, must be submitted to the open-access database PubMed Central upon acceptance for publication. This policy does not apply to non-peer-reviewed materials such as correspondence, book chapters, and editorials.
Some journals will submit your final manuscript to PubMed Central on your behalf, meaning that no additional action on your part is necessary. A list of journals that provide this service is available here.
If the journal publishing your article does not appear on that list, there are two steps that must be taken in order to successfully submit your article.
One last thing: Once you successfully submit articles to PubMed Central, a PubMed Central reference number, known as the PMCID, will be assigned for each article. As of May 25, 2008, in all subsequent work with the NIH (applications, proposals, and progress reports), when citing such PubMed Central papers of which you are an author or co-author, or which have arisen from your previous NIH awards, you must also cite their PMCID.
The NIH has put together an exhaustive FAQ about all aspects of the Public Access Policy.
The Library can help, too! Contact your department's library representative or h [dot] corbett [at] neu [dot] edu(Hillary Corbett), Scholarly Communication Librarian.
View our poster session from the 2008 Research and Scholarship Expo: The NIH Public Access Policy: What It Means for NU Researchers.
View a flowchart on How to Demonstrate Compliance with the NIH Public Access Policy that was created by the Becker Medical Library at Washington University of St. Louis (PDF).