Apple recently shut down it's MobileMe services, including iDisk, replacing them with iCloud. But, iCloud doesn't replace all of the functionality of iDisk; in particular iCloud will only store and sync files made with Apple's productivity tools: Keynote, Pages and Numbers. iDisk would sync any filetype within an iDisk. If you used iDisk as the drive within which all your documents, photos, etc. were stored you could sync any file across all your computers. Since, like many people, I have to use MS Office for work iCloud is basically useless for document syncing.
So when the shutdown of MobileMe was announced last year I went looking for a replacement. Many people recommended DropBox, which Steve Jobs famously described as, "a feature, not a product." However, after some research I chose the less well known SugarSync. After almost a year, I'm very happy with the product. SugarSync will sync files in any selected folders (and nested subfolders) across multiple computers. Dropbox and iDrive make you designate a single folder within which all files to be synced must live. SugarSync also keeps a copy of the last five versions of each file in the cloud so you can easily retrieve accidentally deleted files or roll back to a pervious version. It has a music player for stored music files and special features for photos. There are iOS and Android apps that work very well providing read only access to all files on the move. If you share files with other people they can download them from SugarSync without having to join SugarSync or use any third party software.
SugarSync is actually much better than iDisk was, for a comparable price. An article in The Register claims that Apple, unlike Google and Amazon, really doesn't understand the cloud because managing massive amounts of data isn't where its roots lie. They might be right, because in my experience MobileMe, iDisk and now iCloud really don't quite deliver the usual Apple experience.