Two weeks ago SilverStripe featured at the world's largest open source software conference, OSCON. We gave a talk to a crowded room of software developers titled, Ten Usability Epiphanies for Your Open Source Web-app. The slides are available in PDF and you can watch the entire session online. This will give you insight into how SilverStripe thinks about usability.
After the talk, several people asked for URLs mentioned in the talk, so we've made them available for everyone here:
To be wowed by what is possible with JavaScript, check out the presentation software at 280slides.com, written in the cappuccino objective-JavaScript framework.
Finally, I suggested that d7ux.org is very interesting. This is because it will detail the "before, during, and after" of an open source project going through a major usability effort, with all of the thinking, decisions, and code intended to be out in the open.