Keyboard navigation is no problem in ckeditor, I'm able to navigate btween the different menu bars and other controls. However, many of the formating options cannot be read out by my screen-reader. For example, if I mark this text and press ctrl+u to make it underlined, the editor doesn't give me an audible or braille readable feedback. So I don't know if my formating actions take place in the desired way or if my text gets messed up. That's why I always prefer bbcode or html input over wysiwyg editors. Working with html code might be slower, but it gives me a more exact control of what I'm doing. Maybe in other browsers ckeditor might work better with screen-reading software, haven't tested this. Using the open source NVDA here (http://www.nvda-project.org).
Btw: I've started a editor related topic over in the core dev forum yesterday.
Added 5 minutes later:
OK, the underlined text shows up correctly, but I only can confirm it after submitting the reply.