Something that wasn't mentioned in the change list:
In the preview release Toolbars are now stored as XML files. Existing .dop files will be converted transparently the first time they are changed and re-saved.
This means you can do advanced editing of entire toolbars using a text editor's features such as search & replace and macros. People can now also write programs and scripts to change or generate toolbars without having to reverse-engineer the old binary format.
Of course, if you're going to start messing around and editing the XML, be sure to make a backup first.