Apple made a huge splash recently announcing the iCloud service for iPhone and iPad. Some of the really cool things about iCloud are cloud backup of all your contacts, apps, calendars, etc. For people who want to own and iPad or iPhone but do not want a computer this can be a huge advantage. All of your stuff will be backed up with out having to sink to a computer first. When you get a new phone, all your data will be downloaded to it.
There are some other competitors to cloud computing such as the efforts by Amazon, but they are not as enticing for Apple users as iCloud. iCloud will work with all your Apple devices and will not require any additional effort on your part. All your data will be instantly available on all your Apple products.
I am excited to see this in practice. I currently have 3 Macs, 2 iPhones, and 1 iPad in my family that I am always trying to keep in sync. It will be really nice if the cloud works as advertised and the mundane task of data migration will be handled by the cloud.