I have a laptop hooked up with an extended desktop (using Nvidia chipset and control panel)
I am dragging the VLC window to the extended desktop, starting the video, and then double-clicking to fullscreen. However, when I do this the VLC window maximizes fullscreen to the primary display (laptop screen) and not my extended desktop (TV)
It worked properly in 0.8.6i
Now if I got to Tools > Preferences > Interface and uncheck "Integrate video in interface" it will work but only temporarily. It will fullscreen appropriately for the initial video being played. If I have a playlist and the first video ends and transitions to the second then it will fullscreen back to the primary display.
I hope this information was useful if I can get you anything else please post back.