One of the more under the radar items in iOS, is the TextExpander inspired Keyboard Shortcuts feature. Keyboard Shortcuts allow you to create quick shortcuts, which then expand to larger words or phases. It's a feature that's best used for stuff that you tend to type over and over again, which helps reduce repetition, therefore making you more productive.
In the past with iOS 5, these shortcuts resided independently on each device, meaning you had to setup all of your shortcuts on each device individually. If you do a lot of blogging or other forms of writing on your iOS device, then chances are, you can benefit from having a decent array of shortcuts. With that thought it mind, it's a headache to have to setup each device manually with the same shortcuts.
We already knew that iOS 6 would feature custom dictionary iCloud syncing, but it was never really clear whether or not Keyboard Shortcuts fell within that area. It's been one of the features that I've been saying would benefit from iCloud syncing for a long time now, and thankfully, it looks like Apple took care of that with iOS 6.