I had a hard transition to Android coming from BB, but this app has made me never look back. It learns from your SMS txting history, and you can also link in Facebook, Gmail, and other accounts to provide more content for it to learn. Sometimes I am scared by how well it works. It doesn't just wait for you to type and then suggest/predict your word. It predicts your next word before you even begin typing anything at all. For example, When I start a txt message, it already has "I", "Where", and "When" as options to pick, because apparently those are my top words starting a message. For phrases I use a lot, like when saying goodnight to my fiance over txt, it literally predicts EVERY word exactly how I would say it.
tl;dr - Just buy it. It's the best SMS app on the market.