As an aside, right now I'm using Noia KDE icons, but I'm not that pleased with them -- does anyone have another free icon set they'd recommend?
I'm a big fan of Nuvola (http://www.icon-king.com/goodies.php), which is an LGPL icon set.
Very cool stuff! I hadn't really paid attention to the filebrowser until I saw what you meant in the live demo. The ease of use factor is HUGE. I've since shown a couple people what you've been doing and saw the cartoon iris dialation in their eyes; they were impressed. "I want it!" one web developer exclaimed! Nice work.
point of interface design: i think the mac expansion triangles are better -> unexpanded v expanded blah