SwiftKey is probably the best alternative keyboard for Android. It comes with a bunch of features, most notable of which is text prediction—SwiftKey predicts what your next word is based on what you wrote before. It can learn from your tweets, Facebook updates, text messages, Gmail conversations and/or your blog.
One of the things I love about the app is that it isn’t limited to English. Since I use my phone daily to communicate in three languages, I find it neat to be able to easily switch between them and have it learn the way I type in my current language.
As of version 4, SwiftKey have introduced gesture typing, which is surprisingly accurate. You glide your finger across the keyboard and the app types the desired word. You can also glide your finger to the spacebar, which eliminates the need of ever lifting your finger from the screen of your phone.
Other features I like include themes and smart spaces. The latter inserts a space between two words should you forget to.
SwiftKey is available for both phones and tablets. If you are’t convinced that the app is worth 26 SEK (4 USD or 3 EUR), you can download a free 30-day trial.