Now that iOS 4.2 is out and we’ve lauded its best features, it’s time to take a look at its biggest omissions. (It’s only fair, right?) We took an informal survey of Macworld editors to determine the most-hoped-for features that still aren’t here, then whittled the list down to the top ten.

Better notifications

Push notifications were a welcome addition in iOS 3, letting applications and services notify you—via alarm tones and onscreen messages—of events, updates, and other information. But let’s be honest: iOS’s notifications feature is mediocre at best. Only one notification can appear on your device’s screen at a time—if you don’t get a chance to read or act on a message before another one comes in, you usually end up losing the first. And don’t forget those times you’ve taken your phone out of your pocket or bag and performed the habitual unlock swipe…only to realize there was a notification on the screen that you’ll never get back. Or those times when you’re watching a video or playing a game and a notification pops up—if it’s something that requires an action, you usually have to stop what you’re doing and switch to another app, because if you just dismiss the notification, you can’t go back and review it later. (Did we mention that notifications are modal, meaning you must deal with them when they appear?) As we noted in our iOS 4 wishlist earlier this year, Apple would do well to spend some time with a few webOS and Android phones, which handle notifications much more elegantly.

Improved multitasking

Perhaps the biggest improvement delivered by iOS 4.0 was multitasking, which let you “run” more than one app at a time. But we use the word in quotes because, for the most part, only one app is actually running at any moment in time. Other apps, most of which are essentially sleeping, appear in iOS 4’s multitasking shelf (accessible by double-pressing the Home button) for quick task switching. Apple does provide a few API hooks to allow limited background tasks—such as letting a photo app finish uploading pictures to Flickr, or enabling an audio app to stream music—but apps that don’t fall within a narrow range of functionality are left out in the cold.

Apple hasn’t provided true multitasking because of concerns about performance and battery life. And we get that—in fact, we appreciate it. But now that we’ve had a taste of multitasking, we’d like to see Apple extend the feature to allow for a few other types of tasks. For example, we’d like apps for consuming downloaded content—RSS readers, Twitter clients, news apps, and, of course, Instapaper—to be able to periodically download updated content in the background, rather than making us wait each time we launch them.

Also, the current implementation of the multitasking shelf leaves a lot to be desired. For example, apps stay in the shelf—even if you haven’t used them in days—until you manually remove them. If you tend to use many apps, the shelf becomes little more than an endless string of icons, making it less useful than switching between apps using the Home screen. An option in the Settings app to “Remove idle apps from the multitasking shelf after # hours/days” would go a long way to streamlining the process.

More Mail features

It’s great to see the iPad finally get the best new features of iOS4 Mail: a unified Inbox, multiple Exchange accounts, threaded discussions, notes syncing, and MobileMe alias support. And Mail on the iPhone, iPad, and iPod touch continues to be a solid app that gets the most important things right. But we can’t help but wish that—over three years after Mail first debuted—Apple would bring a few more oft-requested features from Mac OS X Mail onto iOS. Just a few examples include the capability to mark all as read and delete all; send to e-mail contact groups; flag messages; and choose between multiple signatures. More ambitious wishes include on-device folder editing, junk-mail filtering, smart folders, and more control over text when viewing and composing messages.

Better application data sharing/syncing/access

One of iOS’s most significant barriers to productivity continues to be the lack of a robust way for applications to share data and documents with other apps. Apple has taken a few baby steps in the right direction—with iOS 3.2 on the iPad and iOS 4 on the iPhone and iPod touch—by letting apps register themselves for particular types of files (for example, PDFs, Word docs, and text files). That way, when you receive one of those types of files in, say, an e-mail message, you can open the file in one of the apps that supports it. But this is more of a kludge than a solution—for example, if you want to open a Word document in two different apps, you need to save a separate copy of that file in each app. As much as Apple seems to be trying to avoid it, iOS needs some sort of central file-storage area where applications can share data and documents with each other.

Similarly, getting documents and data onto your iOS device is still a pain, and the process differs wildly between apps. Some require you to drag documents in and out of iTunes when your iPhone, iPad, or iPod touch is connected via USB; others sync via MobileMe, Dropbox, or another online service; still others include some sort of built-in Web server that mounts a volume on your Mac or Windows PC for transferring files; and a few support only the e-mail method mentioned above. Apple needs to make this process simpler and provide a way for app developers to incorporate this new-and-improved method into their apps, so that getting documents onto your iOS device—and, just as important, being able to do something with that data once it’s there—is as easy as it is on a Mac.

iCal to-do syncing

Judging by the seemingly astronomical number of to-do-list apps in the App Store—many of them using third-party programs or cloud services to sync with your computer—you’d think Mac OS X and Windows didn’t include any way to track tasks. But they do. In fact, on the Mac, that feature is a prominent part of iCal, a program that otherwise syncs flawlessly with your iOS devices. It’s been over three years, Apple—can we please sync our iCal tasks with our iPhones and iPads?

Wireless syncing

E-mail, contacts, bookmarks, documents—all of these things can sync between your iOS device and your Mac (or at least between your iPhone or iPad and one or more online servers). The amount of stuff you can transfer over the network to your device isn’t slowing down either, which makes the requirement of connecting your iOS device to your computer using a physical cable seem somewhat primitive. We can understand not being able to sync hours of video over AT&T’s cellular network, but if you’re at home, on your own Wi-Fi network, wouldn’t it be nice if you could get the new tunes you’ve ripped or downloaded to your Mac onto your iPhone, without having to plug in? Or update your iPad’s photo albums while sitting on the couch? Wireless syncing could even be restricted to files under a particular size, or capped at a particular amount of data, to prevent saturating your wireless network with tens of gigabytes of data. As we said earlier this year, “Don’t make us plug in our iPhones unless we absolutely have to, Apple.”

Dashboard-like functionality

One of the coolest features of webOS and Android phones is the ability of apps to actually do stuff without being launched. For example, weather apps can display the current temperature, calendar apps can show you your schedule for the day, and sports apps can keep you updated on the latest scores, all by displaying data right on the home screen. We’d love to see similar options on our iOS devices—especially on the lock screen, so we could get whatever info is most important to us without having to unlock and launch an app.

Streaming your media to iOS devices

One of our favorite iOS 4.2 features is AirPlay, which lets you stream media from your iOS device to an AirPlay-compatible component such as the latest Apple TV or an AirPort Express. But we also want to be able to do the opposite: stream media from a source to our iOS devices. For example, a 32GB iPad can’t accommodate the 85GB of music and movies you’ve accumulated on your iMac. But if you could access all that media from your iPad by streaming it over your Wi-Fi network, you might find that arrangement to be just as convenient. (In fact, the Apple TV lets you do exactly this, as does iTunes’s Home Sharing feature on Macs and Windows PCs.) Similarly, we’d love to be able to play, on our iOS devices, music and video on network drives—such as, say, a hard drive connected to an AirPort base station.

There are third-party apps out there right now that provide such features, but they require you to run additional software on your computer, and, of course, you must run the third-party app instead of the iPod app.

AirPrint

Back when Apple first previewed iOS 4.2, the company announced AirPrint, a feature that would finally let iPhone, iPod touch, and iPad users print over a wireless network. A couple weeks later, the company announced details of AirPrint, explaining that the feature would let you print directly from iOS apps to both Hewlett-Packard printers that include the new ePrint feature, as well as to printers connected to, and shared by, a Mac or Windows PC. Unfortunately, full AirPrint functionality is missing from iOS 4.2. You’ll still be able to print to HP ePrint printers, but—at least for now—you can’t print to a printer shared by your computer. (Apple’s official position is simply that with iOS 4.2, you “can print to directly to AirPrint compatible printers without the need to install drivers or download software.”)

Apple hasn’t officially canceled this feature, however, so we’re holding out hope that it simply wasn’t ready—and that we’ll see it in a future update to iOS 4.

A hardware orientation-lock switch on the iPad

Rather than a hoped-for feature that’s still missing, this one is a popular feature Apple removed in iOS 4.2. The iPad’s orientation-lock switch—an actual, physical switch—was one of our favorite features when the iPad debuted. Given the iPad’s versatility, you end up switching it between horizontal and vertical orientation frequently—but you don’t necessarily want the screen flipping around at the slightest movement. So we were understandably befuddled by Apple’s decision, in iOS 4.2, to change this oh-so-convenient switch from locking the screen’s orientation to muting the iPad’s volume.

Why? Our best guess is that Apple wanted to make the iPad and iPhone more similar but, as Lex Friedman so eloquently explained, that’s not a convincing reason: the iPad is a very different device than an iPhone, and on an iPad, an orientation lock is much more useful than a mute switch for many people. (Not to mention that the iPad already had a hardware mute feature: just hold the Volume Down button for a second or so.) We’d like to see Apple restore this button to its original purpose, as the procedure for toggling the screen lock under iOS 4.2—double-press Home, swipe, tap, press Home—is nowhere near as elegant. At the very least, give us an option in Settings to decide for ourselves whether the switch should be for orientation locking or muting.

Runners up

Though we picked the ten not-in-4.2 features that are missed the most by our editors, a number of other features were nominated, as well. Here are some of the more notable ones:

Customizable alerts and tones

Multiple-user settings

Bluetooth data features

iPhone/iPad/iPod touch Disk Mode

Brightness control in the iPhone’s multitasking shelf, as on the iPad

Text-to-speech Caller ID

Voice Control API for apps

Auto-downloading of podcasts on the iOS device

“Quiet time” for push notifications

FaceTime over 3G

Simpler Google Apps setup and integration

Tabbed browsing on the iPad’s version of Safari

App-level Restrictions for third-party apps

Manual mode for syncing with iTunes

Of course, iOS development isn’t stopping with 4.2. Here’s hoping we’ll see these features—and many more we haven’t thought of yet—in future releases.

Edited 11/22/2010, 11:48am to add multiple-user settings to the list of runners up, since the author forgot to include it. (Thanks to commenter RayGaida for the reminder.)