The larger screen also creates a problem: it pushes the Z5's square control cluster to the bottom of the player's face. The Nano's clickwheel is positioned halfway between the screen and the bottom edge of the device, so the wheel sits right below the natural upward-angled position of the thumb. The Z5's control forces your thumb downward. It's not uncomfortable, but I can imagine it becoming so after prolonged use, just as some mobile-phone keypads do.
But that's nothing to the controller itself. Samsung has attempted to come up with something that apes the iPod's clickwheel. Since it's gone for a square layout, it can't use the simple circular motion of the iPod. It hasn't even opted for the up-and-down motion of Creative's vertical touchpad. Instead it works by tapping.
Apple's iPod Nano and Samsung's Z5: clickwheel vs clicksquare
I found it slow, and not always accurate. After a while, I realised that the arrows printed on the pad are merely for guidance, not to represent buttons. What you should do is tap anywhere in the upper half to go up the menu, and vice versa. But I assume the clearly marked central area was the equivalent of the 'select' button - as it is on the Nano. Not so - for that you have to press the pad firmly. Just tap the central zone and your input could be interpreted as an up-arrow or down-arrow press, depending on how close to the centre you are.
It's all quite frustrating until you get the hang of it, and even then it still pales beside a true scroll control. There is a scroll mode: tap and hold, and the cursor rises or falls automatically, but it's not obvious. How many sales are Samsung going to lose as consumers desperately tap away on demo models trying to get the Z5 to play?
Samsung says it works better with a fingertip tap rather than a full-finger press. That's true, but it's not much consolation for folk with big thumbs. Pressing the touchpad or the Back button generates a neat UI transition in which you move into and out of the screen through each semi-transparent menu layer. It's cute, but it doesn't get you to the next screen any faster than Apple's UI does.