Comment 5 for bug 995039

I think it's a shame and that this issue hasn't been addressed since 11.04. I love Ubuntu and Unity but this is single most frustrating thing I'm experiencing right now.. Even in a humble Win XP on my work PC this feature works like a charm..

BTW, as a workaround, I suggest to using a scale plugin. After grabbing a file/item to be dnd'd, I initiate window picker by moving a mouse to a screen corner (or other preferred location), then hover the pointer over the desired window until it gets a focus, then drop. Note that key bindings do not work for some reason. You need to assign a region on the screen to be activated by the mouse pointer (scale plugin, bindings tab, initiate window picker --> BottomLeft, TopLeft).

This works actually quite well, but I anticipate a proper solution/fix from Ubuntu team.