The changes in Beta 7 are mostly user experience enhancements that are meant to make it easier to get started with the bigger Ethereum experience. Additionally, this version includes a much requested feature; the ability to import Presale Wallet files without having to do all sorts of command line gymnastics.
The purpose of this user guide is very focused: To help newcomers install and use the official Ethereum-Mist Wallet App to manage their ether. For the time being, that’s it. As such, I will avoid describing those enhancements/features that do not directly relate to this objective.
The release notes for version 0.4.0 (Beta 7) are found here.