Most recently, we published MCPE 1.2 – Better Together update which you can download right now. This update has become the largest in the history of the pocket game, someone is still finding new features that did not exist in previous versions.
As for version 1.2.1, it is a patch – fixing a lot of serious errors found in the early days that are a problem for gameplay. The full changelist is on the official website of Minecraft, if you want to see it, click on the link.
You can download all versions of Minecraft PE 1.2 and participate in the improvement of the game, send the found bugs through the feedback form and probably they will be fixed in the next update.