As a developer of websites for clients, I have a huge concern over the functionality being added here. For blog posters, there's no doubt that Gutenberg will be a boon, but for the websites that I develop, it will be hugely detrimental to have my clients adding all sorts of layout options to areas of the page that, in order to remain consistent to the design and functionality which I have developed for them, shouldn't have.

If the various components of Gutenberg can be managed by me then it won't be a problem - I'm thinking to have a filter or action that I can use to turn off, for example, the full-width content blocks, or multi-column blocks. Even better would be to disable the whole thing and revert back to the simple text editor. At the moment, I'm not a fan!