I just added theme support for Gutenberg's wide image feature, and I'm writing this post to see whether it works, and also just to see how easy it is to simply sit and write something in Gutenberg at its current version. (What is its current version? 1.81)
I had to tinker with the CSS because Twenty Seventeen has a very narrow post content area and a right sidebar, so making wide images fill the entire viewport width doesn't work. But wide images now show up wider than the content width.
It seems I can create a wide gallery, too.
The embed list looks much more complete than last time I was here.
Alas, I don't really have time to go through all the blocks now. I think Gutenberg is looking pretty good, though it really seems to save a metric shedload of revisions.