The tab "Edit & Advanced features" now features some extra usability enhancements. "Wide document background" enables the textareas and RTE areas to have the width adjusted according to the width of the viewport. Default the width of these areas is pretty narrow. Previously this option could be set by typoscript only, but can now conveniently be checked in User settings.

Two very usable additions are: "Make Textareas resizable" and "Make Textareas flexible".  The first option makes the textareas resizable by dragging the lower right corner of the textarea with your mouse. The flexible option makes the field grow automagically as you type.