I really want to play with this, one of the main problems that I'm having is that if you don't know which direction the object was moving, say it was going up,

I really want to play with this, one of the main problems that I'm having is that if you don't know which direction the object was moving, say it was going up, and you're dragging down would it do anything? And in one frame you could be holding on to something whilst in the next you're holding nothing... I guess we'll have to play with it to see how the interface works. I kind of get the feeling that it will be like placing the OS X dock on the right or left side of your desktop, you instinctively want to resize by moving up or down, but you have to move left or right.