Apple first announced iCloud service back in June, it will allow users to virtually store various files includes iTunes and documents in the Cloud, Photo Stream, cloud backup in cloud and this service will replace mobile me. iCloud.com website also now live, you can log in to this service with your apple ID.
Apple finally removed the Beta tag from iCloud and Apple also pushing out iOS 5 later today; iCloud will help you save more space on your PC or Mac by storing content through the cloud infrastructure.
I think better you go for iOS 5 ,that is going to be released later today. Along with iOS5 you will be getting 5GB of free iCloud space with you Apple developer account. If you want lot more space Apple got $20, $40 and $100 options where you will get 10GB, 20GB and 50GB extra storage respectively.