The one gripe I hold with the current UI is the massive bar at the top. Of course keep it there as default as I'm sure many enjoy it but as I highly value my screen space the ability to toggle it would be great.
A suggestion I can live without would be instead of the drive bar, you could have a drop-down box residing in the leftmost part of each path bar. Again, I'm just a fusspot when it comes to screen space.
That aside I'm really impressed with you work here. It's clean, responsive and above all, it does what it's designed to with ease and intuition. Keep up the good work!