Just been using this for a client for the first time and while it's not perfect (what is) it's brilliant at what it does. I've just made a template for a client (they sell guitars and that online) which they can then go in and edit the content - picking what products they want to feature, including the product name, description, link and image and send it off themselves, without any interaction from us - unless they specifically request our help.
Would still recommend using CM itself for anything overly complex, but for content-managed emails I doubt you'll find anything better than mailbuild.