Its very difficult but addictive! Apparently the US Air Force use something like this as part of fighter pilots training. They are expected to do it for over 2 mins, if you get above 18 seconds you're doing really well.
Let us know your times. My highest at the moment is 15.42 seconds.
Ive played this before, and gets me every time. It best not to be played while eating Roast Chicken with your Fingers, cus it makes your Mouse Slippery.