If Apple were to re-tool iCloud in a few ways they could have an amazing service that provides great value to their customers:
a) Email: The iCloud email service is workable and has no ads (unlike Yahoo and Gmail) though their is not compelling reason to switch away from your current email provider (particularly if you've been using that address for many years). Apple should allows users to set-up their domain name with iCloud email service at no cost, and hassle free. While other services are available for hosting domain specific email many solutions are unwieldy for small businesses or independent professionals.
b) Document(s): iCloud allows for document syncing/storage for Pages, Numbers, and Keynote documents though the marketshare for those applications is small in comparison to other document formats. As there are several alternatives for document storage like Google Drive, Dropbox without the application limits Apple could re-tool the service as flat cloud storage and also provide greater security than other services. Apple could provide full encryption for uploaded files, and for extra-points provide options for complete privacy where even Apple can't access the file contents. (This furthers Apple's stance as a strong advocate their user's privacy.*)
*For an amazing look at the security Apple has built into their iOS products I highly recommend episodes 446-448 of Security Now on the TWIT netcast network.