Speaking of camera improvements, it's now possible to use the digital zoom feature when snapping photos on older models, such as the 3GS. While a digital zoom is no substitute for optical zoom -- if you go too far, your pictures get pixelated -- I'm willing to bet that many users will find it useful.
The Photos app now supports Faces and Places, two features found in Apple's iPhoto software. Faces can track photos based on an individual's facial features. Places supports geo-tagging, which groups photos by location on a map. Both will help iPhone users better organize and sift through their photos.
The iPod music software has also gotten some minor tweaks. For instance, in iPhone OS 3.x, the Album view listed a Shuffle option first, and then featured a simple song list. But the new iOS 4 displays more information when a specific album is selected, including album art, release date, song count and overall length, plus a Shuffle button -- all at the top of an album's song list. The list of songs in the Album view displays more information, too, including a subtle gray coloring behind song titles, a track number, a speaker icon indicating which song is playing, and track length in minutes.
Mail now supports e-mail threads, storing e-mails with similar subject lines in a unified list, allowing for better conversation tracking. And the Mail app now supports a Unified Inbox, allowing you to keep track of all of your e-mail in-boxes in a central location.
Other enhancements include the aforementioned on-the-fly playlist creation; external bluetooth keyboard support (similar to what's in the iPad); Game Center for gamers; Location Services control on a per-app basis; the addition of Bing as a search option; Calendar support for iCal birthdays; support for iBooks, including newly added PDF, notes, bookmarks, and automatic remembering of your spot across multiple devices like iPhones and the iPad; new luscious home screen wallpapers that should look stunning on the new iPhone 4's retina display screen; character count in the SMS app; and -- finally -- support for Internet tethering from AT&T.
A side note on tethering: Normally, this would be included as a major feature, if not for the fact that it's crippled by AT&T's pricing structure, or the fact that this feature has been out for more than a year for iPhones on better carriers. Thanks, AT&T.
Hundreds of new APIs for developers
While I've focused here mainly on user-facing features that arrive with iOS 4, there are hundreds of back-end improvements that will allow developers to produce even better apps for both the iPhone and the iPad. Here are just a few examples of features developers can add to their apps: iPod remote control accessories, in-app SMS messaging, spell-check, photo library access, Quick Look for document viewing, full map overlays, access to still and video camera data, access to date and address data detectors, and access to Calendar data.
In other words, if you appreciate the breadth and depth of the still-growing number of applications in the App Store, you can expect them to get better as developers adopt these new functions and add them into their apps.
Final thoughts
Apple's iOS 4 offers a number of compelling reasons for users to upgrade, featuring performance and app enhancements that are well worth the price. That price? It's free for all of the hardware devices that can run it (even the iPod Touch). Upgrading should be simple: Plug your iPhone or iPod Touch into your Mac, launch iTunes, and click Check for new software. Follow the prompts and you'll soon be ready to see for yourself.
Is iOS 4 the pinnacle of smartphone technology? Of course not; there's still a lot of room for improvement. (For starters, an organized notification screen for alerts would be really useful.) But the new features and tweaks in this update -- in concert with the fact that Apple is giving the software away -- make this upgrade a no-brainer.
Michael deAgonia, a frequent contributor to Computerworld, is an award-winning writer, computer consultant and technologist who has been using Macs and working on them professionally since 1993. Find him on Twitter at @mdeagonia).