OneDrive is my default storage location for almost everything on my PC. I've stored photos I've shot on my phone (Since HTC HD7 days), my documents all go there, memorable videos (niece's first steps etc. and family events). I've also backed up all the ebooks I still had, my ringtones, any research I'm working on, case studies and my brain's backup OneNote work's there as well.
Short answer is I'm using close to 65 gigs.