As much as like the now look, something very important for me is gone. I guess it is similar to the account overview for other. I only have one mail account but I sort my mails on server side in several folders. The old k9 gave me the option to choose a start folder or None. I had None and therefore, when opening k9 I saw a list of all folders with the number of starred and unread messages. One overview of everything.
Now I always start in the inbox. So I have to open the side menu to see all the other folders. I would like to start with that side menu open to choose a folder. And I would like to open a folder in “only new messages” and “only starred messages” mode. That was very useful to read old, but still important mails without scrolling down and searching for them.