This new interface puts the controls of the various filters (sliders, curves, etc...) directly in the main window, instead of using separate dialogs. The idea is to reserve an area below the layer list, where the controls of all the selected layers are shown sequentially (in the same order as the layers).
Each group of controls belonging to the same filter has a sort of "tool" bar, where one finds buttons to toggle the visibility of the layer, activate/deactivate the layer mask, activate/deactivate the preview of the current settings, and to reset all the controls to their default values. The tool bar also contains an editable field with the layer name, and an expander button that shows or hides the rest of the controls.
Here is a preview of the new interface (with two layers selected):
As you can see, there is still a lot of work to do, but the interface is I think quite clean and intuitive. Would you have any suggestion, do not hesitate to drop a comment!
A new tutorial under construction
Meanwhile I've been also busy putting together a rater long tutorial on panorama editing with Hugin and PhotoFlow. It is almost completely written now, and should soon appear on pixls.us! Keep an eye on this blog, the google+ community or directly the pixls.us forum, as we'll certainly drop a message when it will be finally online!