Apple packs iOS 4 with decent punch

The iOS 4 release appeared Monday, weighs in at about 300 MB for the iPod touch and nearly 400 MB for the iPhone. It's free for all devices on which it works.

It can be installed only by launching iTunes, selecting your mobile device, and click Check for Updates. The iPhone 4 comes with iOS 4 preinstalled, and

iOS 4 cannot be installed on an original iPhone (2007) or first-generation iPod touch (2007). The update works with all other models of iPhone and iPod touch.

Multi-tasking, keyboard support, wallpaper, and a few other features work only on the iPhone 3GS and third-generation iPod touch, both released in 2010, as well as the iPhone 4.

The launch of its latest device

Apple paired the launch of its latest device, the iPhone 4, with a significant mobile operating-system upgrade for owners of 2008 and 2009 iPhones and iPod touch players.

The new system, iOS 4, is the fourth mobile release for Apple and demonstrates that with maturity comes incremental rather than revolutionary change. You'll still recognize the old iPhone OS with its new iOS moniker.

Middle ground

Apple chose a middle ground by defining specific kinds of things that apps can do when they aren't frontmost, including continuing an in-progress Internet phone call (VoIP), playing music, updating the location of a navigation app, or completing a download. This compromise lets Apple optimize battery and memory use, along with performance.

Programs can also pause when a user switches to another app. In iPhone OS 3 and earlier, when you press the Home button, the current app quits, but developers could save your place.

Since the iPhone was announced in January 2007, pundits, owners, critics and Amazonian tribespeople have asked about a keyboard, preferably internal. Apple's desire for a clean interface dominated by touch seemed to keep even an external keyboard at bay for years, but the company finally buckled.

An Apple Bluetooth keyboard can be associated with multiple devices, although I found it tricky in an office where one was paired with a Mac, an iPad and an iPhone to choose the device I wanted. The Mac kept grabbing the keyboard connection first.

Picture taking (all iPhones) and video shooting (iPhones 3GS and 4) has been improved by dramatically speeding up the time between tapping the picture icon in the Camera app and a picture being captured. You can tap to focus while taking videos (previously limited to photos), and a 5x digital zoom is available for pictures and video.

The iPod app

In the iPod app, iOS enables creating playlists directly on your device, instead of being stuck with lists created in iTunes and synced to the phone or iPod.

Those who have the iPhone 3G (2008 model), like co-columnist Jeff Carlson's wife, have found iOS 4 makes that model sluggish. On an iPhone 3GS, I found iOS 4 improved responsiveness.