David Wiley wrote that quality of any learning resource whether it be commercial or OER must be measure based on the learning that occurs.

See: http://opencontent.org/blog/archives/2947

I agree with David that the quality of learning resources should be judged by the learning outcomes,achievement levels of the students who use the material.  I would also agree with gpouliot that graphic design and/or the lack of it can have an effect on the student learning outcomes. But there are also other “quality” measures that point to superiority of OER. These include OER’s superior “sharability” where sharing of content/ideas/methods etc. can be as effective as good graphic design in improving learning outcomes. “Timeliness” is another advantage of OER; when they are on the web, students don’t have to wait to access their course materials. Moreover, the course materials can be updated by the teacher and students whenever needed. I believe that “usability” is perhaps the strongest quality measure and OER beat commercial content ‘hands down’. OER can be used by a wide range of devices, learning management systems, applications without restriction. “Accessibility” for learners with disabilities is also augmented by the use of OER that do not suffer from digital locks. Commercial content all too often has a kill date. Once the course has finished, students must delete the content from their devices (if it is not done automatically by the publisher). “Extensibility” of OER beyond the course is  the norm – students can keep the content as long as they like. OER also have greater “reach”, in that they are available to many users over great distances and in different jurisdictions for many different uses. Cost-effectiveness is another excellent quality measure. If the students can’t afford the cost of the resources, then quality issues don’t even matter. If content A is free as an OER and it can produce equal learning outcomes to content B, which is commercial and is expensive, this can be a quality indicator. These are all quality measures that should be considered in evaluating learning resources.