I have accounts with ALL of these. I use these services to backup specific files to the cloud as well as keep the two computers I use daily in sync. So documents that I create on my iMac computer automatically get copied to my laptop computer and visa versa. Not only that, each of their iOS apps allow me to access and share my documents from my iPad and iPhone.
I use DropBox to backup my computer's most important work files. DropBox is my most valuable and most used cloud storage service. I do pay for additional storage but it's well worth the price for backing up my computers and keeping my files in sync.
I use Google Drive to replace Microsoft Office. So mostly letters, spreadsheets, and presentations. I also use Google Drive to collaborate and share files with my clients when working on projects.
I use Box as my "Downloads" folder. Box will give you 50 GB of free space if you download their app. A no brainer. I set all of my web browser's default download folder to a Box folder so I can easily access the files I download from the web from any computer. Nice tip!
I use OneDrive for... nada. I have no use for this one. I simply opened an account to check it out but because I don't use Microsoft products, I have very little use for this service at the moment.
One great service not mentioned in the article is Flickr. I use Flickr to backup all my photos. They offer 1 TERABYTE of storage space for free! That's enough space to backup every photo you've ever taken in your life. My iPhone is set up to automatically backup every picture I take to Flickr so I basically have unlimited storage for photos accessible on my phone.
It's nice to know all my files are backed up and accessible in the cloud. If one or even both of my computers broke, I'd still have all of my important files. And that helps me sleep good at night.
Go read the article and try them out for yourself. Happy computing.