Having been using the CMS more from a content editors perspective than as a developer recently, I've come across a few niggles which I'd like to point out, in the hope that this will assist in making improvements to the design of the CMS editing tools and overall user experience.
1) I would prefer the "Navigation Label" field to be moved to the "Metadata Tab". I find that having two (usually identical) title fields is mildly jarring, and in the common case, is not actually useful to me. Perhaps other people do find this useful, but I find it detracts from the focus on this screen, which is the rich text editor. Bringing me to my next point...
2) The rich text editor for page editing is not tall enough for longer content pages. The space feels constricted, and involves a great deal of scrolling. I simply find the ration of height to width on this content box far too skewed towards the width, and it's not as comfortable as it could be. Also, if there is a "fullscreen" button on TinyMCE, I couldn't find it. FCKEditor has this, and it works rather well.
3) A more esoteric problem that I have been running into, because of my keyboard muscle memory... When cleaning up imported paragraphs, I quite often hit Apple-Left-Arrow to skip the cursor to the end of the line. This inadvertently causes the browser back button to be triggered, which skips back a page, and I lose all my unsaved edits.
Will post more feedback as I notice things...