Love it. I usually use a slip bag and then punch it hard so it moves around quickly to train evasive movement as well as accuracy. Slip bags are nice because they can be made out of almost anything (the one I'm using right now is just a jump rope I tied up to an extendible suitcase handle I stuck on top of a cabinet - you punch the handle), but I might actually like this better if you already have the double end bag.
