I'm looking at a few of the programs you mentioned.
Julia
Some influences: low cost, open source, friendly user interface, flexibility of multiple presentations of content to meet program requirements & provide for end user creativity & alternate uses, broad user/development community, ability to build communities from within institution and external to the institution, ability to tag content, ability to export as a website, ability to support a range of artifacts/file types, having the tech expertise for install—luckily we had in-house expertise in terms of Brent Lee (mentioned in another thread in this Seminar)—and resourcing for tech support/training via my position in addition to the instruction/training via courses taught by the faculty.
Challenges: buying a server (done) to house content---a few IT hoops to jump through from an institutional perspective; training faculty; need to determine phases of roll-out; getting faculty to refer to assignments in terms of where/how they could be used in a portfolio as a common practice through every course; designing & developing the templates we want to create
Before Mahara--when I started with students this year-- I gave students a choice to present their portfolios as web page, using Moodle via a course shell we developed for eportfolios, via the LiveBinders site http://livebinders.com/ , Voice Thread http://voicethread.com or other tool/platform.