Dropbox has a really polished, easy-to-use cloud storage product going. Having used it both personally and professionally, I have been able to use it sync seamlessly across multiple devices (PC, Mac, iPad, iPhone). Their product really is intuitive, mimicking Windows Explorer (on Windows) and Finder (on Mac) so the user can basically move the files around like they normally would. I have also been able easily share files with colleagues and friends without any issues. There's not much more I can ask for in a cloud storage product.
