Fresh from seeing a secret panoramic photo function inside iOS 5, we've now heard that enterprising hackers have found another feature — predictive word lists above the keyboard. Android and Windows Phone users will be familiar with this design, with suggested words appearing above the keyboard based on the letters you've typed. It's been reportedly tested on both the iPhone 4S and iPad 2, but should be available across all iOS 5 devices. As with the panoramic photos this doesn't require a jailbreak, just a backup of your device, and software to expand that backup to allow you to edit Apple's preference list files.
Besides the added row of words, the Go / Search button is replaced by "confirm" allowing you to select what you've typed and move on. However, there's no auto-spacing, so you'll always have to select the word from the suggested list or hit confirm before hitting the spacebar and starting the next word, which might explain why the feature hasn't been included in this release. If you want to try it (it's reversible), there are instructions in the source link below.