iOS 5 is now available to the public after having been teased for months. Unlike the last major update to the operating system (iOS 4), we think iOS 5 could be the most significant update to the iDevice line since the rollout of iPhone OS 3 back in 2009. Why do we say that? Simple—because of the sheer number of new and improved features that make the iPhone, iPod touch, and iPad more usable than ever.

We're talking significantly revamped notifications, Twitter integration, wireless sync, iCloud, home screen improvements, and more—so many, in fact, that we can't address everything buried within an app or setting in a single review. What we will do, however, is talk about the major updates as well as those tidbits that interest us the most after having used the OS. We did run across a few nitpicks here and there that we hope Apple addresses in future updates. Overall, though, we think it's worth upgrading to iOS 5.

Notifications

The push notifications introduced in iPhone OS 3 (which we'll refer to as iOS 3, for consistency's sake) were helpful at the time, but only because they were better than nothing. The notification system has long been a sticking point for users who were seeing more robust notifications show up on competing platforms—namely, Android. Under iOS 3, every new SMS or push alert showed up as a modal dialog box in the center of the screen, forcing the user to make a decision immediately. The system also offered no way to see multiple notifications at once—and certainly not on the lock screen, which was essentially useless (except as a timekeeping device) until this point.

Now, however, all that has changed. Apple has completely revamped how the OS handles and displays notifications from its own apps as well as from third parties. Three areas are most affected: the settings, the lock screen, and what Apple calls the Notifications Center.

Settings

The notifications settings will tell you most of what you need to know about how they work. The main settings screen lists every app that could send you notifications, and you can control how each app uses them.

A typical app will let you switch its Notifications Center alerts on or off. You might also have the opportunity to choose how many notifications from that app to show.

The Alert Style settings let you choose how you want each app's notifications to appear—this will be when you're already using the phone and a notification rolls in from the Messages app or a Twitter app, for example. The "Alerts" style is the old notification style, with the item in the center of the screen and buttons for you to acknowledge the notification immediately. The "Banners" style is new—it rolls down a banner from the top of the screen with the relevant information, but goes away automatically after a couple seconds if you don't do anything to acknowledge it. When you do tap to acknowledge the notification, the phone takes you directly to the app in question and (hopefully) directly to the message or item that is currently asking for your attention. Finally, the "None" option is for those who want to see notifications on the lock screen or in Notifications Center, but who don't otherwise want to be interrupted by that particular app.

The last two settings are obvious: do you want badges on your app icons showing the number of unread items? (No, thankyouverymuch.) Do you want to see these on your lock screen? Depending on the app and on your personal preferences, you may choose to have some of these show up and others not—our only wish is that Apple would somehow make it possible for us to universally turn on or off a certain type of notification (such as no more wire hangers badges, ever!)

Notifications Center

The Notifications Center is where you'll be able to find all your notifications. From anywhere within the OS or even various apps (they don't have to be Apple apps, either), you can tap and then pull down from the top of the screen in order to see what needs your attention. In the above example, I have the weather turned on, plus a new iMessage, an appointment on my calendar for later in the day, and two undoubtedly losing moves to be made in Words with Friends.

Tapping on any particular notification will take you directly to that item inside of its related app, e.g., tapping on a calendar appointment will take you to the calendar, tapping on the Words with Friends moves will take you to that game, tapping on a Twitter message will take you to a particular message within a Twitter app. The items that can be dismissed—that is, those not calendar items or the weather—will remain until you tap the X to clear out the notifications for that category. Because of this, I pick and choose what shows up in my Notifications Center screen (and also my lock screen) very carefully; I don't really need to see that 25 new people sent me @replies on Twitter, but I would like to see when I have a missed call or voicemail, especially since I turned the badges for those apps off in the settings.

Generally speaking, Notifications Center has worked great for me, but I have run into a problem with notifications from some (admittedly not very important) apps. One is Words with Friends—though the notifications do seem to show up for me occasionally, they don't always. Many days, I can open up my Words with Friends app to see that several friends are waiting on moves from me, but the alerts won't be in my Notification Center despite the settings clearly stating that they should be. It's not obvious to me whether this is a communication problem between specific apps and the OS, as this doesn't seem to happen for the majority of the other notifications that I have set up (and never with Apple apps).

Those familiar with Android can recognize immediately the visual similarities here; in fact, some of you have been falling all over yourselves to tell us about it ever since Steve Jobs showed off iOS 5 notifications during the 2011 WWDC keynote. Certainly, Notification Center in iOS 5 looks and acts much the same as you might expect to see on a modern Android device, and that's apparently because it's a design that works well. I rarely have personal qualms about any one company mimicking the basic designs of another, but Apple will probably want to keep an eye out for the patent lawyers on this one, as the lawyers are a feisty bunch nowadays.