NEW YORK (AP) — Apple's iOS 8 software update for iPhones and iPads is worth getting — but not necessarily right away.

Those with an older device, such as an iPhone 4s or an iPad 2, might want to wait to see whether others have difficulties using iOS 8 with slower processors. Some of the new features won't be available on those three-year-old devices anyway. It might be time to get a new phone or tablet instead.

Even for newer devices, some apps might not be fully functional at first. Dropbox, for instance, says there's a problem with a camera backup feature. Specialized apps you have for work might also be affected.

And a new feature for tracking health and fitness data isn't working because of a software bug, so Apple has been removing affected apps from its app store. Apple says it hopes to fix the problem by the end of the month.

Meanwhile, some Mac integration features from the past might not work until Yosemite comes out. That is especially true if you activate Apple's new storage service, iCloud Drive. Even if you get iOS 8, you might want to wait on activating iCloud Drive on your device. Your phone or tablet will warn you before you activate it.

Once you upgrade, it's very difficult to go back.

And when you do, be sure to back up your photos and other data first.