Note: This review is a reprint from Macworld US. A UK-specific review with the iPhone 3GS tested against O2's network is underway.

In slightly less than two years, Apple’s iPhone has transformed how the world thinks of cellphones. Phone companies and hardware-makers alike have rushed to ape the iPhone’s touchscreen interface, easy access to the Internet, and bustling App Store. The iPhone is no longer the mind-blowing, category-busting product it was in the summer of 2007. Our minds have been blown, the category was busted, and now competitors such as Palm, Google, Nokia, and Research in Motion are fighting back.

In the face of the stepped-up competition, it’s possible to consider Apple’s new iPhone 3GS a minor step forward for Apple. After all, it looks almost identical to its predecessor, which itself offered very few changes from the original iPhone model. But with the iPhone 3GS, combined with the iPhone OS 3.0 Software Update, Apple has addressed all of its product’s key weaknesses while adding several important new strengths.

Yes, the competition is much closer to Apple now than it was two years ago. But the iPhone 3GS makes it clear: Apple is still leading the pack, in most cases by a wide margin.

The S is for “same”

Externally, Apple hasn’t messed with success—the iPhone 3GS is almost completely indistinguishable from the original iPhone 3G model, which itself was remarkably similar to the original iPhone. Front and center is the iPhone’s signature feature: a bright, beautiful high-resolution 3.5-inch diagonal touchscreen, offering a resolution of 480-by-320 pixels. The iPhone 3GS has Apple’s usual complement of four physical buttons (Home just below the touchscreen, sleep/wake up top, a volume up/down rocker on the left side, and a ringer toggle just above the volume controls) and the same black or white plastic back shell introduced with the iPhone 3G.

If you need to know which model is which, there’s only one clear way to do so: Look at the lettering on the back of the phone. If it’s in the same silver ink as the Apple logo, it’s an iPhone 3GS. (Likewise, if 32GB appears below the word iPhone, you know it’s an iPhone 3GS—the previous model was only available in 8 GB and 16 GB editions, while this phone’s capacities have doubled to an impressive 16 GB and 32 GB, allowing users to load their phones up with even more apps, tunes, and videos.)

Beyond the color-matched lettering, which shows a uniquely Apple-like attention to detail, the only other change to the outside of the device is the addition of an oleophobic coating to the device’s touchscreen. When Apple designed the iPhone to be controlled entirely by touch, the company has had to deal with the unpleasant reality that human beings tend to secrete oil from their pores, as well as stick their fingers in greasy foodstuffs from time to time. The iPhone 3GS’s screen coating is intended to keep fingerprints to a minimum.

I’ve never really found fingerprints to be a major problem with the iPhone, since the device’s screen has always been quite bright. But it’s undeniable that in the right lighting conditions, fingerprints can really get in the way—especially when you’re trying to watch a video.

The iPhone 3Gs’s oleophobic coating doesn’t make your fingerprints magically fade away. What it does is create an oil-repellant surface that’s easily wiped clean. When I handled an iPhone 3G and an iPhone 3GS with similarly oily hands—olive oil, if you must know, from a pizza I was making—I was rapidly able to dump my grubby prints all over both devices’ touchscreens. After I rubbed the iPhone 3GS screen onto my t-shirt’s right sleeve, it was perfectly clear. In contrast, rubbing the iPhone 3G’s screen on my t-shirt’s left sleeve seemed to leave a thin film of oily residue spread uniformly across the entire surface, rendering everything a bit hazy.

Will people buy the iPhone 3GS because it’s got an oil-repellant screen coating? Certainly not. But in adding the coating, Apple combats a weakness—albeit minor—in the design of the iPhone. Given how few changes Apple made to the iPhone’s exterior, this is clearly a company that feels great confidence in its current product designs. Instead of revamping the phone’s look and feel, the company’s designers are instead focused on the little things, like making it easy to wipe off greasy fingerprints.

That said, I have to point out that many iPhone users choose to protect their iPhone’s screen from hazards more noxious than oil by using some sort of screen protector. When you see those people on the street, whatever you do, don’t say the word oleophobic. It will just remind them that this is one feature they’ll have no use for.

NEXT: The S is for “speed”