What makes this keyboard unique is its TouchType Fluency prediction engine, an amazing text-prediction technology that is said to be able to correctly predict about 33% of words without any letters being entered and about 80% with just 1 or 2 letters entered.
I installed it on my HTC EVO and have been very impressed by how much I don't have to type. You can set it so that pressing the space bar will accept the predicted word that appears in the middle of the bar above the keyboard, which I find to be faster than tapping the actual word but it definitely takes some getting used to. I'm so accustomed to just typing normally that I initially found myself typing more slowly on the SwiftKey keyboard so that I could keep an eye on the prediction bar. It feels very strange to just tap the space bar to enter whole words, but I can see what a time-saver it can be once it becomes second nature.
See it action in the video below or download it from Android Market to try it for yourself.
I'd like to see a face-off between the fastest SwiftKey and Swype typists.