A nice interview (with discussion in the comments) with John Willinsky, author of The Access Principle: The Case for Open Access to Research and Scholarship.
Q: Many publishers argue that journals and materials for which one must pay are somehow by definition of higher quality than various open models. How do you respond?
A: The empirical evidence argues otherwise: For example, the Public Library of Science (PLoS) Biology, a relatively new open access journal that operates on author fees, has the highest “impact factor” (number of times articles are cited) by a considerable margin among biology journals indexed by the ISI Web of Science. But that is only part of the quality story. The majority of journals now allow their authors to “self archive” their published articles in open access institutional repositories (usually located in the author’s university library). But note that in all cases, someone pays, though it is not necessarily the reader, and these alternatives are greatly increasing access to this knowledge.