First of all, this new release is only compatible with XenForo 1.2.0 and above.
This new version brings a couple of new features, check out the updated screenshots in the Resource Description.
1) Add-ons can now be built without specifying any directories. This effectively just packages up he XML file into a ZIP. This is useful for add-ons that only require the XML file but still need to be uploaded here as a ZIP file (e.g. TMs).
2) Removed dependency on a third party Helper to recursively build ZIP files. (It now uses Zend Framework).
3) As well as building the add-on and creating a ZIP file in the build directory, it is now possible to download that ZIP via your browser upon creation.
4) The default path for styles has been changed. It assumes that your images will be in the default @imagePath location (styles/default) and in a lower case directory that matches the add-on ID.
5) There is no longer a separate page or Navigation item to choose the add-on you want to build. This is now integrated in to the main add-on list.