The problem with that editor is that I cannot (easly) add table support to that editor and it must be configured in a way to load some specific Newsletter plugins.
So actually I cannot move to that editor.
Lately WordPress is making the internal editor usage more easy, but I have to study the api and understand how I can add the tinymce plugins I need.
I use an older version (2.5.2.6) – a special version with german translation. In this version there is no button for selecting an image with the media library.
I tried the the latest version and I see the button you mean, but I can’t use this version without configure anything new. Is there any other possibility to integrate this button?