Another downside is that it’s a single point of failure.
You might think so but I found out otherwise. A couple years back, I lost my iPhone - in a really unique way, I'll have to tell the story someday. When I got my replacement phone, it downloaded all my information, including address book, apps, music and all the settings. It was like I had my phone back.
Turns out all your data is actually replicated "up in the cloud".
So losing your device is not the catastrophe it used to be.