I have been looking at Helen Barrett's pages and there is some excellent and thought-provoking material there. She is based in teacher training, but she raises many philosphical issues that we need to consider. I would especially recommend reading this entry in her blog about choosing an eportfolio system - it incorporates her view of what an eportfolio is (and can be), and analyses the competing forces that come into play when eportfolios are being set up. Reading this should help us to clarify exactly what (and who!) we want this system set up for, and help us to focus on what the student experience might be.
And here is another article from 2004 that she wrote with David Gibson about these issues, and (relevant to us) detailed suggestions about how to assess portfolio software.
Here is a graphic which compares assessment management systems with electronic portfolios. This is one of the philosphical problems that Barrett identifies - the need to balance quantitative assessment reporting systems with qualitative experiential measures of learning.