Fred Dylla has published "Three Years after the OSTP Public Access Directive: A Progress Report" in The Scholarly Kitchen.
Here's an excerpt:
So three years out from the directive, 1) public access policy is in place for 98% of the research funding from US federal agencies starting in the last year, 2) a robust article identification system is in place from Crossref that is already tracking more than 11,000 funding agencies worldwide, 3) CHORUS, a public-private partnership, is actively assisting the agencies with implementing their public access plans, 4) TDM solutions are beginning to appear, and 5) agencies, supported by various stakeholders, are making some headway on data management.