Updated to 18 on Mac OS and iOS and it’s great.
One surprise—my Markdown headings are no longer changing color except in the “light” theme (first on the list). I’m fine with waiting for the future update where we can monkey around with the theme ourselves. But I do really like having a good dark mode theme where my eye can instantly pick out headings. I do see that if I go to multi markdown I’m keeping what I was used to. I also confirmed this when the same draft was giving light blue headings before updating and monochrome as soon as I updated to 18.