Here's what it does: It lets you use gestures to type, meaning you can continuously slide across letters to make a word and just lift your finger to make a space. It also autocorrects your errors, predicts words, and lets you tap the microphone to compose messages using your old talk box.
Google's new version is like many of the alternative keyboard titles you're already familiar with, which are necessary because Android phones all come with their own crappy proprietary keyboards, except of course for the Nexus 4. But across the board, it's generally not a great experience. However, Google Keyboard recreates the stock Google goodness on any Android phone. We're not sure how it stacks up to other keyboard replacements yet, but it is customizable to whatever flavor of Android you're rocking. [Google Play via Android]