A few comments on the button which invokes the side pane:
- In Firefox on Mac OS X, the scroll bar partly overlaps the button, making the experience slightly less polished: http://imgur.com/1nBcjd1
Should the button be shifted a little to the left?
- Why not retain the same icon with a toggled style to it, instead of replacing the icon with a close-button icon? Has there been any discussion around this?