Valerie Spezi et al. have published "'Let the Community Decide'? The Vision and Reality of Soundness-Only Peer Review in Open-Access Mega-Journals" in the Journal of Documentation.
Here's an excerpt:
Findings suggest that in reality criteria beyond technical or scientific soundness can and do influence editorial decisions. Deviations from the original OAMJ model are both publisher supported (in the form of requirements for an article to be “worthy” of publication) and practice driven (in the form of some reviewers and editors applying traditional peer review criteria to OAMJ submissions). Also publishers believe post-publication evaluation of novelty, significance and relevance remains problematic.