I’m in the same camp as @Shamino. I used to use it because I liked being able to indicate important stuff by giving it a background color in my usual column view layout. But when they switched to tags that background color became a little LED next to the item. That essentially broke what I was trying to do. So I stopped using it. In Mail it still works the old way and there I still use it too. Of course there I miss that it obviously doesn’t sync over IMAP so its usefulness cannot extend beyond one Mac.