The new buttonless iPod Shuffle, which moves all the controls onto the headphone cord, is taken to task in this article:
The new iPod shuffle: Button, button, who's got the button?
Now, I'm a recent purchaser of the previous Shuffle model, and intuitively I prefer the Play/Pause/Forward/Back/Up/Down controls of that previous model. But I like to take contrarian positions sometimes too, so let me see if I can defend the new Shuffle from a UI point of view.
One thing I notice with the older square Shuffle, is that each time I clip it on requires a mental orientation session. With this jacket, it's clipped on this side; with that shirt, it's clipped on the other side with the controls upside down and reversed; with a t-shirt, it's probably clipped on the bottom, and so the controls are 90 degrees from either of the previous orientations.
This takes a few seconds, which isn't a long time, but it's annoying if the goal is for the player to vanish from my consciousness. I quickly straighten out which button skips to the next track, but if I'm too distracted to visualize how the Volume Up/Down buttons are situated, I might find which is which by trial and error while driving. Plus I may clip it in a different orientation if I decide it's more important afor this outing to turn it on/off, vs. having easy access to the audio jack.
Now, there are a few ways this could be addressed. Some sort of Braille-like bumps to make the buttons distinctive to the touch. A rotating control area -- probably wouldn't help without the bumps. An accelerometer to make the buttons swap functions when it's clipped up, down, or sideways. But all of those just drive the cost of parts up, and still take some getting used to.
Having the controls on the headphones, regardless of whether you like earbuds or not, does make the interaction identical however you clip on the actual player -- in the car, walking, working out, in your pocket, upside down during weightless space training, and so on. (Actually, could you even plug it in to a car stereo without some kind of extra adapter cord with the new controls?)
I think there's a much broader lesson to draw here about Apple's UI principles. Lately, it's introduced lots of things like the Shuffle, the Apple Remote, the single giant button trackpad. The theme here is "Fitts's Law". Broadly speaking, it means that it's easier to select something UI-wise if it's big and nearby. I like the AskTog description better than the Wikipedia article:
AskTog: First Principles of Interaction Design
You see this principle applied a lot in Apple's software UIs. Think about the magnification of icons in the dock as you mouse over them. The thing you might select is directly under the mouse, and it gets bigger so it's hard to miss. Or the software keyboard on the iPhone, where you tap a letter that's very small, yet the screen displays a magnified version of each letter as you type it, so you can slide your finger to adjust if you didn't hit quite the right spot.
Now, the principle is bleeding over to the hardware side of UIs. IBM had the little mouse nub for Thinkpads. Right under your fingers as you were typing, but small and hard to hit or control. The Apple trackpad that's all button, all the time, is a purer expression of Fitts's law. You could even say it embodies a third related principle, that in addition to making the item easy to select, you arrange the UI so that there's only one logical action for this one giant button to perform. So you're not clicking on different parts of the trackpad to do different things, it's always "select"; other gestures, such as double-clicking or the two-finger swipe, are physically different, but again work regardless of the location.
We see this new principle spreading in the world. For example, the video players you see on web sites where the initial screen is a single big Play button. We saw it a while back in hardware with that third-party gizmo that was a dial with a single button. These days when I use a second monitor for Photoshop, I realize it's part of the same trend; this monitor is really a UI control with a single selection -- its own On/Off button, to select when entering or leaving the mode where I need more screen space for menus and palettes.
But anyway, back to this new Shuffle. We've got the controls that are situated in the same location regardless of how the device is positioned and oriented. We've got a single action that the controls perform, with less-frequent variations that depend not on location but on a different gesture (double- or triple-clicking, press and hold). So, although I still like my el-cheapo headphones and cassette adapter for the car, the new Shuffle UI makes sense if considered part of a pattern.