Apple iCloud is a great place to share files. This is especially true if you are a multiple Apple device user. iCloud enables sharing data seamlessly across all of your Apple devices.
As a backup solution, iCloud well serves iOS devices (iPhone, iPad). iCloud backup is designed into iOS (and iCloud) and iOS devices are programmed to restore themselves from iCloud, given valid iCloud credentials, when reset.
iCloud isn’t the best backup solution for Mac and isn’t designed to be. You can mirror the content of your Documents folder. Pictures and other media can synchronize across iCloud. For Mac, Apple offers time machine backup. My take on time machine backup is that it is best used with a physical data store wired to your Mac with USB-3 or firewire.
Here’s what Apple has to say about backing-up your Mac.
More than that, iCloud storage is subject to subpoena. If you have great faith in the legal system, that isn’t going to bother you. Depends on the judge and the motivations of the (mostly invisible, barely accountable shadow) parties requesting the subpoena.
One thing you can do is create an encrypted archive of your data and store that on iCloud. Be prepared to wait a long time for that archive to fully upload to or download from iCloud. It’s not iCloud so much as a bandwidth problem– the speed of your internet connection. Most of our archives will be pretty large.
So you might or might not find iCloud suitable. It’s extremely convenient for synching contacts, keys, and other data across Apple devices. It’s a great backup solution for iOS devices.