The latest iPod Nano combines the larger screen of the third-generation Nano with the slender design and vibrant colours of the second-generation models. Taken as a whole, the fourth-generation iPod Nano marks the further evolution of an already-strong media player, but it will disappoint anyone who was expecting a complete overhaul.

The 8GB model sells for $149 ($50 less than its predecessor), and the new 16GB model comes in at $279.

The iPod Nano is almost identical in height and width to its second-generation grandparent, bucking the wider-but-shorter design adopted for the third-generation model. When I saw the new iPod Nano, the first thing I thought of was the flash-based Zune from Microsoft. The screen's portrait orientation means you must turn the Nano on its side to play video; but since the Nano now has a motion sensor, the video orients itself properly depending on how you hold the Nano. Turning the unit on its side for video works well, though not as well as it does with the iPhone or the iPod Touch because having the screen on one side and the navigation wheel on the other makes the iPod Nano seem out-of-balance.

The iPod Nano has a slender, tapered design. At its thickest point, the iPod Nano is 0.24 inch thick — a barely perceptible 0.06 inch thinner than the previous model. The new iPod Nano is also about 0.5 ounce lighter than its predecessor. The latest version also ushers in brighter, more vivid case colours — a departure from the muted tones of the previous generation. Since the Nano itself has a curved face, the glass that covers the screen is curved, too; during normal use I didn't notice any distortion caused by the curved glass cover.

Audio sounds adequate through the included earbuds, though you may want to upgrade to Apple's forthcoming, step-up $80 earphones or to a high-quality pair from a third-party manufacturer.

You have good reason to upgrade your headphones: According to our tests, the latest iPod Nano improves its audio output as compared with its predecessor, jumping up a notch to receive a rating of Superior on the PC World Test Center's suite of audio tests. The Nano, together with its new Touch sibling, are our new leaders in our audio output results.

If you have used an iPod before, you won't notice any huge differences in the latest iPod Nano's interface; the new version retains the familiar menu system and wheel-based navigation. Apple did, however, introduce some cosmetic changes to the menu system, primarily so that it works better when used in a portrait-screen orientation. The biggest change involves the Now Playing screen, which displays album artwork at full-screen size, with the song's title and artist information in a narrow strip along the bottom. From a functional standpoint, the Now Playing screen doesn't bring much innovation to the table, but it does look more attractive.

The new iPod Nano incorporates Apple's Genius algorithm, which enables you to create Genius playlists. Hold down the center button while at the Now Playing screen, or while selecting a song, and a floating menu will pop up. When you select 'Start Genius', the Nano will generate a Genius playlist on your iPod, just as iTunes does. Save the playlist, and it will remain available on your iPod; then, the next time you sync your iPod with your computer, it will add the playlist to iTunes. As I mentioned in my review of iTunes 8, Genius playlists are spot-on when it comes to identifying music that goes together well.

One new and welcome feature is the ability to create voice recordings. You'll need a separate microphone adapter — or a pair of headphones with a microphone, like the ones that Apple will soon be shipping. This feature was missing from the third-generation Nano. Still missing, from all iPods: an FM tuner.

The most gimmicky of the new iPod Nano's features is the ability to translate physical shaking into a shuffled playlist: You can shuffle the Nano by shaking it, and you can reshuffle the unit by shaking it again. I found that mastering the shaking motion was a little tricky: I had to shake it reasonably hard to get shuffle mode to kick in. Unfortunately, I didn't have a chance to test whether shuffle would inadvertently kick in while carried on a jog or worn at an aerobics class. The feature may be useful if you're out walking and want to switch to shuffle mode without fiddling with menus — but you may get a funny look or two. Shake-to-shuffle might be fun to show off to your friends, but I don't see it as much more than that.

Once again, Apple put together a great media player with the new iPod Nano. New/old shape aside, however, it is a fairly minor update with only a couple of interesting new features. But like iTunes 8, the new iPod Nano doesn't venture far into previously unexplored territory that might have made it a must-have device.