I have been regularly using Ubuntu One for a number of months and I have been beyond impressed with the quality of their free service.
Ubuntu One is essentially your link to a personal storage cloud for all of your content and best of all Ubuntu One is available on multiple platforms and their free plan provides more storage than most of the other services out their including Dropbox.
For me using Ubuntu One is a no-brainer simply because it comes integrated into Ubuntu but if your one of those Windows fanboy’s you can still use Ubuntu One since there is a Windows app available.
I use Ubuntu One to securely* backup all of my documents and occasionally some important photos I want to keep but since I have a iPhone I’m really considering using the Ubuntu One Music for iPhone App which could be practical for me when I’m on the go.
With Ubuntu One offering more space and more peace of mind than Dropbox and mind you with the security concerns over using Dropbox I honestly do not know why someone wouldn’t decide to make the switch.
I would love to hear any feedback whether positive or negative on your experience with Ubuntu One.
*Ubuntu One does not encrypt your data by default however if you use encryption on your file system which I highly recommend then your data will carry over in a secure fashion.