Apple's more important release last week was not the new iPhone 4S. It was the new iOS 5 operating system for older iPhones, iPads and iPod touch models, which add up to a much bigger chunk of the portable-gadget market. And by addressing many of the worst oversights of earlier releases, iOS 5 does far more to advance the state of mobile computing.

The best part of iOS 5, judging from three days of testing on an iPad 2 and then an iPhone 4, is its notifications system.

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Instead of interrupting you with a pop-up dialogue for each new text message, email, voice mail or other nag, iOS 5 confines most of these alerts to small banners that don't block what you're doing. You can see a list of these items by swiping down from the top of the screen — as you would in Google's Android, except iOS 5 doesn't also keep a count of unread notifications there.

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Apple again follows Google's example in cutting the cord. After one last massive download and installation through iTunes, a task often frustrated by Apple's overloaded servers when iOS 5 debuted on Wednesday, you no longer need to tether an iPhone or iPad to a computer to set it up, synchronize data, back it up or install iOS updates. But since activating online backup of the iPad via Apple's free iCloud service took two days, while earlier Apple ventures into cloud-based services flopped, I'm a little nervous about the reliability of all this.

Other smart additions in iOS 5:

• The software adds a "Tweet" option to the standard sharing menu. Android users, who have long had a choice of social-media shortcuts in their sharing menus, may find that familiar.
• You can do basic photo editing and, by pressing the home button twice, take pictures without unlocking an iPhone. (Does the second item remind you of anything, Windows Phone 7 users?)
• On the iPad, Safari works more like the desktop version of Apple's browser, with tabbed browsing and helpful single-page-view and reading-list options (but, so far, without Safari for OS X Lion's exasperating habit of force-reloading pages).
• A Newsstand folder groups newspaper and magazine apps, which can now download new stories in the background.

These changes all work for me. But a few aspects of iOS 5 look sloppy.

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Take its new Reminders app, which lets you create to-do items that become active when you leave or arrive at a certain place. Fantastic idea! But if that place isn't your current location, it must be in your contacts list. Do Apple's developers habitually add grocery stores, malls and airports to theirs?

Its iMessage program upgrades text messaging by adding delivery confirmation, group conversations and indications when correspondents are typing. But by limiting this to iOS 5 devices — not even a Mac can take part — Apple fails to challenge the carriers' expensive text-messaging services.

Then there are the features Apple didn't ship in iOS 5. Its search feature still doesn't scan the street-address or notes fields of contacts (a failing shared with Android); you still can't send a file via Bluetooth wireless (my Palm Treo 650 did that in 2005); worst of all, its maps app still can't provide turn-by-turn navigation, bicycling directions or any of the other extras available in Google's Android equivalent.

This is a fine update overall, one you shouldn't hesitate to install on a compatible device (older iPhones and iPod touch models aren't eligibile). But it also leaves me wondering if Apple's been reading too many of its own press releases.

Credit: Rob Pegoraro/Discovery