this is a minimalist content editor, but so far it has proven reliable. a bit rough still, but reliable. and versatile too. :)
have not tried writing a post on iPhone 5 with this yet, but it should be doable.
uploading a Post, begins with a Stream dropdown choice. after selecting the Post archetype, select the image file.
after upload a new archetype is created for you. head on to the content editor and edit the new draft content.