In reply to Matt.

Thanks for this response. This seems to clarify a few things for me. If Gutenberg will be all that when it is shipped, it will be an improvement.

And if there's a large enough transition period.

What seems to be missing right now is a clear roadmap and explanation for how the transition period will look like, what developers need to do, change and learn, what will change exactly, how developers will need to convert existing code to new code, etc. I think a reason there's so much resistance and negativity around Gutenberg is that for many Gutenberg came very sudden and it's development pace seems to imply an "almost ready" state (0.9!), without any of the conditions I mentioned above.

The revised roadmap of Jan 2018 is only a few months away. I have like 50-70 clients websites which could break with Gutenberg, relying on custom post types, custom fields, meta boxes, plugins using those, etc. Imagine the work that needs to be done to convert all that code. Many months of work. Let alone imagine the problems I will have convincing clients to pay for all that. They will not be happy.

A transition period of at least a year or two will be needed in my opinion.