It seems that when you float a DockingWindow it doesn't work with Aero Snap i.e. when you drag close to edge of the screen, or press Win+Left or Win+Right. Visual Studio 2010's floating windows work OK. I did some investigation with Spy++ and it appears to be the WS_THICKFRAME window style that controls this behavior - I confirmed this by modifying the style of a DockingWindow with FindWindow/SetWindowLong and Aero Snap started working, but I don't know if this will have any unexpected side effects. Are there any plans to fix this?