The 2009 volume of the German Yearbook of International Law features a contribution by Michael O'Boyle, deputy registrar at the European Court, & John Darcy, entitled 'The European Court of Human Rights: Accomplishments, Predicaments and Challenges', pp. 139-180. For those interested in comparative approaches, the same volume also includes similar essays on human rights challenges in the other regions of the world. The yearbook is unfortunately not available online, but can be found in most academic libraries. The publisher is Duncker & Humblot in Berlin.
Many thanks to EM for notifying me of this!