iCloud as a service has several aspects, of which Dropbox-style file sync is only one. I actually don't use that part AT ALL, in part because I was an early adopter of Dropbox and continue to find it meets my needs well, even when I have to use Windows.

However, iCloud is the best choice for me to use to sync what we used to call PIM data between desktop and mobile devices.

iCloud for iOS backup has also been really good to me. I trust it fine. But I also trust that all the key data being backed up to iCloud from iOS is also being backed up from my desktop or by other means, so I mostly just use iCloud for "pim data" sync and, obviously, to move into new phones when I buy them.

Had my phone stolen. Bought a new one the next day. First boot took several minutes but when it did boot, everything was there - all my documents and pictures, all my apps, all my preferences and settings (not only for the phone itself but for each app too), even the background image and app icon layout was the same. IIRC I didn’t even have to re-login to many apps, just the security-conscious “trust this new device?” ones.

Such a seamless backup and restore experience is remarkable in and of itself, and I don’t think if Apple allowed third-party backup services they would get to that level of seamlessness. I don’t know for sure that Android (or Windows/Linux, same seamless backup on Apple laptops) don’t have a backup service with a comparable levels of seamlessness and thoroughness, but I don’t think they do.

iCloud backup is a genuinely impressive service and I have to respect it.