Do you plan to add the dock location helpers from Visual Studio 2005 to the docking framework? Currently dragging windows around sometimes requires 1-pixel accuracy and lots of intuition to make them go to the right spot. Visual Studio 2005 added small floating tabs that appear when you drag a dockable window around so you can drop the window on one of the tabs and it will go to the right place.
They use one tab near each side of the window, and a "cross" in the middle of the current drop-target window for easier placement relative to other docked windows. When you drag the dockable window onto one of the tabs, VS fills the destination with a dark blue so you can see where the window will go before you drop it (better than just the outline). Do you have any plans to add this feature?
BTW--We are already a customer and love this toolkit!!