It's also a marketing moat because it raises questions for customers when competitors don't have similar report cards -- what are they hiding? The low-pressure copy and honest voice are a big help, too. Very clever indeed.
I think transparency is a huge competitive advantage. And like you said, it works great as a marketing tool AND as a tool for accountability. There are several ways you can do this but probably the easiest is to just sign up for a service like Pingdom (which is great b/c it injects a 3rd party measurement into the equation) then use their status page tool. We did ours using a twitter widget, pingdom's status page, and some CSS, and I think it turned out OK: http://www.getadministrate.com/status/
