I spent some hands-on time with the new handset at the Apple event. I'll start with the visuals: It's stylish. Whereas the iPhone 3GS looks and feels plasticky, the iPhone 4 is svelte and has a premium feel. Surprisingly, it achieves that impression while retaining the same general design, although the edges appear a bit more squared than before.

iPhone 4It's noticeably slimmer than the iPhone 3GS, measuring 0.37 inch deep versus the iPhone 3GS's thickness of 0.48 inch (that translates to 2 percent less). The iPhone 4 is also slightly narrower, 2.31 inches to 2.44 inches. The weight stays the same at 4.8 ounces, but the tweaks to the dimensions make the current iPhone 3GS seem downright kludgy in comparison. (See all iPhone 4 specs.)

However, it's the aesthetic design touches that make the iPhone 4 stand out. The overall design screams elegance, from the rounded, individual volume up and down buttons that replace the plastic volume rocker on the iPhone 3GS to the ring/silent switch and the power/sleep button up top. The face and back are made of glass that is specially treated to withstand scratches and oily fingers, according to Apple. The side edging is aluminum, and doubles as the device's three cellular and wireless antennas.

Sharp Display

Of course, the iPhone 4 isn't just about cosmetic enhancements, pleasing as they are. What makes this phone such a technological improvement is what's inside the handset.

Like its predecessor, the iPhone 4 has a 3.5-inch display. But the new phone's display doubles the resolution to a 960-by-640-pixel IPS display. At 326 pixels per inch, this is the highest resolution available on a phone to date.

iPhone 4

That display truly makes a difference. Whereas the iPhone 3GS's text, in the menus, in apps, or on web pages, appears thick, fuzzy, and undefined, the iPhone 4's text is razor sharp, even when enlarged (as I tried doing when viewing a PDF).

The new "Retina display", so named because it surpasses the number of pixels the human retina can process, also greatly improves the sharpness, clarity, and visible detail of images.

In both cases, I'd liken the magnitude of difference to that between a standard-definition 80p DVD and a high-definition 1080p Blu-ray Disc: When you view both on an HDTV, the differences are striking. And once you see them, you can't go back.

The real value of the new display will become evident for people who spend time reading on the iPhone 4. I expect the display will make reading a more pleasurable experience (although, clearly, limits will remain given the inherently modest screen size, modest at least as compared with handsets such as the Sprint Evo 4G, which has a 4.3-inch screen, and the much larger 9.7-inch iPad screen).

iBooks Goes Mobile

The high-res display, coupled with the addition of iBooks on the iPhone 4 (and with iOS 4 upgrades), makes the iPhone a more relevant e-reader. iBooks retains its structure, appearance, and function from what we've already seen on the Apple iPad and with this OS's ability to sync the iPad, desktop, and iPhone, readers gain the flexibility to move seamlessly among devices. This capability is available for Amazon's and Barnes and Noble's respective e-readers, as well, but not for other competitors.

iBooks also gains a few new features previously unavailable on the iPad. You can now create notes and bookmarks, and see those notes, bookmarks, and highlights in the table of contents. I suspect that the notes remain trapped in line, for example, there's no way to create cheat sheets, summaries, or other such personalised shortcuts that you could then utilise on your computer or elsewhere, but these new functions are a step in the right direction.

The major new feature in iBooks is its native support for PDFs. You'll find tabs for both books and PDFs. Each one gets a bookshelf or list view (your choice). You can add PDFs via email or Safari, and PDFs can sync back to iTunes and to other Apple devices such as the iPad or iPod Touch.