The quick answer, at least in my experience and usage case, is yes.
This all came up a couple of weeks ago when someone asked me on Twitter what I used to backup my Windows systems.
My answer was that I do not use any backup process except for storing all of my personal files in OneDrive. Of course, all of those files are available to me across my various Windows 10 devices because I use a Microsoft Account to sign into each of them. In addition, I can even access these same files on my Android LG Nexus 5X and an iPad without issue using the OneDrive app.
Now I understand this is not a process that will work for everyone nor would diehard supporters of backing up your device agree. In fact, if you prefer to back up your entire Windows system so that you can restore it intact including installed software and apps, then just using OneDrive is not going to work.
Another situation that might impact this choice is your email stores. Since all of the email I access is online and stored on that server, I just locally cache a certain portion of the mail for faster access. If I have ever have to reset a device and add the accounts back there is a data cost to downloading those cached emails again but for me that works just fine. Another benefit is that it keeps everything in sync between my various devices that access those email accounts.
You will find settings within the latest OneDrive sync client on Windows 10 that will let you redirect your Documents and Pictures to OneDrive. There is also an option to save Screenshots from your device to OneDrive and to automatically sync any images/videos when you connect a camera or similar device to your machine.
Another reason this works for me is that Windows 10 comes with an option to reset your device which supports retaining your data and settings but losing all of your installed apps and desktop software. The process is very fast and can fix a misbehaving system and restores the system to the way it is when first setup. All you have to do afterwards is reinstall your apps from the Windows Store and your desktop software which you can either download from the web or keep backed up on an external drive. These days the vast majority of desktop software is available online and easily accessible for re-installation.
I do remember when I was stationed in Italy and had just a 64KB ISDN connection to the Internet though. I used to save every single download but that is simply not such a necessity these days.
An aspect of OneDrive to keep in mind though that makes it different to backups is that the service syncs your files between systems. A deletion or addition on any device that you access OneDrive with will be replicated on all of your other devices. However, if you accidentally delete a file it can be recovered for a period of time through the OneDrive website in the Recycle Bin folder.
The OneDrive client also allows you to selectively choose what folders are synced to each device that it is installed on and this is very handy for me. One example of a folder I do not sync on every device is My Music where I have over 22GB of files stored and it only gets synched to my main desktop.
I have been using this method for a few years now and am yet (knock on wood) to experience a major data loss. That is more than I can say when a hard drive failure resulted in my wife losing several chapters of a book she ahs been working on for a few years. When something like that happens you figure out a way to protect your data and for me OneDrive is that method.
What tools do you use to protect your important data?