Something not especially practicle with it (granted it's beta so funny things expected)
Say you make some programmable modules for email and you add them via content more
and you see something like
Now say you want to a layout like
Full Width Image
Plus Section
Full Width Image
It allows you to add different images in both the top and bottom Full Width Image module but renders only the top modules content for both when doing an email preview.....
so say you did something like
Full Width Image (populated with a green image)
Plus Section
Full Width Image (populated with a blue image)
You'd get
Green Image
Plus Section
Green Image
So unlike pages where a module can be reused multiple times on a page to render different content. On email it seems to only use content from the first instance of a module and copies it each time that module is used.