We have been avid Mac users since 2009 - and iCloud delivers on it's promise. Update a calendar on one device - and it syncs across iMac, MacBook, iPad and iPhone. The same with contacts. Add a contact on one device and it syncs across iMac, MacBook, iPad and iPhone. No redundant multiple data entry - eliminating typos on one device and therefore "different" data between devices. How did we ever live without iCloud any way??!!