Ended up having too many customization problems with Summernote and Angular on our current project and switched to Quill (http://quilljs.com/) instead. Both are pretty good projects though, and each have room to grow into something bigger.
We went with CKEditor instead, and while it is extensible and the developers are responsive, it is a LOT of work to integrate with JS-heavy front-ends. They use setTimeout() liberally, and don't recover gracefully from ascendant DOM changes. (like being removed from the DOM without being destroyed). That said, it is the most feature-full, open-source editor in active development...
The state of web-based editors is... a mess... and there seem to be new ones popping up constantly, while old ones go stale. So, yet another generation of young devs whose time will be wasted solving the basic, known problems of contenteditable, while quill, scribe, wysihtml, goog.wysiwyg, aloha-editor, tinymce, ckeditor, redactor and likely a dozen others need help.
(and what I really want is ace or kix... a content-editable-less editor)