At this moment I enjoy the sharing and storing possibilities of my Dropbox account and since I got my HTC one S the amount of available storage increased to 25Gb (for 2 years). I share documents and files with my wife, family and friends. We use it for sharing files between members of our local Scouting club, etc.. And even with it's ease of use it's not enough to silence that nagging feeling: it's not your own storage.
When I find the time I think i'm going to do testsetup of Owncloud. It's free and it runs on your own server/storage.
http://owncloud.org/
For those seeking a cloudstorage option for Windows and Linux (no Mac support yet), try Ubuntu One. It gives 5 Gb instead of the free 2Gb at Dropbox.
https://one.ubuntu.com/
When speaking of cloudstorage I feel obliged to mention one of the granddadies of cloudstorage (before we started calling cloud to anything remote or a bunch of servers together) : iFolder. Developed at Novell, released in 2001 and now a open source project.
http://ifolder.com/ifolder
