We have a major warning to share with iOS users. Today is the day that Apple is making iOS 8 available to the public. There will be a number of reasons you will want to get iOS 8, but during the installation it is absolutely critical that you do NOT upgrade to iCloud Drive when the iOS 8 installation prompts you. This is especially important if you also use a Mac as your personal computer. The reason for this is because iCloud Drive will only sync with devices running iOS 8 or OS X Yosemite (which hasn't been officially released yet). The full official version of Yosemite is expected in the next month or so. We are sure there are several of you who may be trying out the pre-release, but we must reiterate that iCloud Drive is NOT COMPATIBLE with iOS versions 7 and older, and it is NOT COMPATIBLE with OS X 10.9 Mavericks or older. Additionally, if you mis-click this option, you will not be able to go back and undo this decision. This is why this article is so emphatic. Of course, if you are running the pre-release version of Yosemite, and you are able to upgrade all of your devices to iOS 8, then you can use the iCloud Drive option. You just need to weigh this carefully for your needs. We have verified this with several sources. Here's a quote with more details from one of them, Above is a pic which shows you the precise step in the installation where you need to make this choice. During this step of the iOS 8 upgrade process you will see an option for iCloud Drive. You simply need to select "Not Now." After that, all of our iCloud data will still be accessible and all of your iCloud-enabled apps and content will continue to sync with all your iOS and OS X machines. Thanks for the tip, @twerppoet!