Apple's decision to transition from the fat third-generation iPod nano to the new svelte fourth-generation iPod nano must have been an easy one. The latest version has the same size screen (just rotated vertically) and the same video support as before, but adds a much more comfortable (sorta) oval shape, a curved screen, an accelerometer, a 16GB version and most importantly, a much improved user interface that aims to solve some of the limitations the Clickwheel has compared to the iPod Touch and iPhone UIs. This evolution succeeds beautifully.
The very first thing you'll notice is how much better the curved aluminium body feels in your hand, even compared to the very similarly shaped 2G nano. The brushed metal feels great, looks great, and is much less scratch-prone than the shiny silver backing in the 3G fat. It's also thinner, because it tapers off to the sides, but it's as thick at its thickest point as the entire body of the previous generation. There's slightly more glare from the screen because it's curved to be flush with the surface, but that's nothing you can't live with. Aesthetically, it's a lot nicer looking than the previous flat screens.
Pocket-ability is definitely important in nanos, and it's less conspicuous in your pocket than the 3G fat version. Unless you have really tight pants and have your pockets up to your stomach, you will most likely not even notice the difference between the two. But if you do do this, watch out. The sharp edges on the top and bottom—a result of constructing the body with one piece of metal and having caps at the ends—are likely to draw blood when scratched directly up against the flesh. So let that be a warning to you, shirtless guy who has his really tight pants hiked up way too high.
An added accelerometer also brings some iTouch/iPhone functionality to their little brother, which is well integrated where it makes sense. Rotating to landscape mode is as fast as it is on the iTouch/iPhone, and the subsequent Cover Flow view is baby butt smooth. Games, which were on the nano before, can also access motion-sensing. The built-in marble maze game is as good as the ones we've seen in the App Store. The "shake to shuffle" feature picks a random song when you jiggle the nano, but is smart enough to not skip tracks if the screen is off or if the hold switch is on. You can of course disable the thing entirely if you're listening to music on a bulldozer.
The portrait UI is also a great improvement over the the fat nano landscape UI, and makes much better use of the available real estate. (The older nano rather awkwardly tried to fit two columns on the screen. This only has one.) The new menu and display fills up the entire top half of device, which gives you more list items at once. Scrolling through menus and Cover Flow is as fast as we've seen on any iPod.
On-the-fly genius playlist creation, which recommends music already on your device based a starting point of any song in your library, worked well. When generating one from MGMT's Electric Feel, genius recommended The Shins, Arcade Fire, Radiohead, Beck and Damien Rice. Not exactly the same genre or song type, but someone who listens to MGMT would be likely to enjoy all these other artists. And that's the point. Apple's basing their recommendations not off of analysing the individual tempo or features of a track, but off of purchasing history and many customers' music libraries. It's too early to say whether this method is better or worse than Pandora's, but it's good enough.
The new nano also comes with a quality Voice Memo app that works just like the Belkin devices currently on the market. It's too bad that you have to pay US$29.99 for a pair of headphones that actually have a mic on board; the default ones are just standard earbuds. Voice notes to yourself, with the microphone just hanging from your ear, is plenty loud enough to understand exactly what you say. Recording conversations with someone across the table isn't as good, but if you pump up the volume you can make most of it out. Clicking the centre button also inserts "chapters" into your recording.
This generation comes in nine colours, which include pink, purple, black and silver, but no white. It's also the first nano to use solely USB charging, so old Firewire chargers are rendered useless. This evolution is naturally the best iPod nano yet, and you should have no hesitations in picking one up. [Apple iPod nano]