Man, am I loving iOS 8! It has so many cool new features I can’t begin to name them all. One of my favorites (in addition to Favorites) is Predictive Text. It takes a little getting used to but I am using it extensively in Messages and a few other places as well.
Here is a screenshot of Predictive Text in Messages on my iPhone 5s
Predictive Text not only guesses at words for you it does so very intelligently. It is context sensitive. For more on how it works check out this YouTube video.
As you can see, Predictive Text is totally useful like a lot of other things in iOS 8.