1. There are plenty of new features to play with
Apple called iOS 8 its biggest update ever when it first introduced the system in June, and it's true that nearly every core application gets some substantial new features. Messages, for example, will now let you mute noisy group conversations -- and will let Apple users send short audio and video clips to each other. Mail now offers you more swipe gestures, so you can archive, mark as read and flag messages more easily. It also lets you keep drafts on hand, so you won't have to save and exit a draft if you need to check another e-mail for reference while writing a message.
Apple's also made changes to its camera software to give users more manual control over how their pictures look, with greater control over focus and exposure. The new system also gives users a time-lapse photography option. And even Siri gets a bit of a boost, with a new ability to listen and write at the same time. Users can also now wake Siri up by saying "Hey Siri," but only when the phone is plugged in -- making it not a very useful feature, as Engadget's Brad Molen notes in his review of the system.
Apple said Wednesday that a software bug will delay release of apps that work with HealthKit, such as Carrot Fit, MyFitnessPal, WebMD and AskMD. The company said it hopes to restore them to its app store by the end of the month.
2. It also lets apps talk to each other
Apple developers are pretty excited that iOS 8 gives them more free reign to have apps work together, rather than having to make users pop in and out of separate apps to do one task. For consumers, that could eliminate some steps -- for example, you can share links straight to your cloud drive of choice from the browser, rather than having to copy-paste into a separate app. This tweak to the system also means that iOS users will get access to different keyboarding apps that have long been popular on Android, such as Swype and Swiftkey.
It also means, of course, that there will be more reasons to opt-in to data collection and data sharing in the name of convenience. For some types of data, such as health information, Apple has taken care to add additional privacy safeguards. But for others, it will be up to users to keep track of which apps they've granted which permissions.
3. It will make your phone play nice with your Mac
One of the biggest features for true Apple fans is that iOS 8 will let your Mac and your iOS device interact more deeply with each other, thanks to a feature called "Continuity."
Thanks to Continuity, users will be able to easily share files between their Macs and iPhones or iPads -- you can even use a feature called "Handoffs" to start reading an article on your phone, and then pick it up later on your Mac. Macs will also now be able to take calls and deliver your text messages, regardless of whether your conversation partners have Apple products or not. Just note: these new features will only work with Apple's forthcoming Yosemite Mac operating system, which is available in an open beta and due for full release this fall.
4. It doesn't work with all Apple devices
Before you rush out to upgrade, make sure you can. Apple phases out support for older devices with each update, so not everyone will get access to the newest system. The oldest devices that iOS 8 will work with are the iPhone 4 and the iPad 2. Fifth-generation iPods are also compatible with the new system, as are both models of the iPad mini.
Once you've established whether you can download the new system, make sure you're ready to. Back up the data on your phone to iTunes so that you have a safety net in the event things go haywire while you update. And if you have a work phone, check with your IT department to make sure that they're ready for you to take the plunge into a new system.
5. It could take a while to download
Every year, Apple's servers get slammed with customers rushing to upgrade their phones to the newest operating system, leading to horror stories about two-hour download times. If you can bear to wait, it tends to be faster to upgrade while plugging your device into your computer and getting the download through iTunes, rather than over WiFi. But, if WiFi is your only viable option, then be prepared to plug in and wait.
Early adopters should also remember that the first round of all operating system releases tend to have bugs, so keep an eye on your battery life for the next few weeks. And be vigilant about downloading new updates that come down from the server, in case security flaws come to light and need to be patched.