Once an image is added to a post, clicking its edit button brings up a two-tab box with assorted edit options. These have steadily improved over time and are now quite powerful and useful. Yet one thing would make them better:
In the "Advanced Settings" tab, where we can manually enter width and height, I would like to see an checkbox where we can enter one or the other and check it to "maintain aspect ratio."
For images wrapped around text, the percentage resize tool works fine. But if we know our theme's width limits - which is where we'd be using this tool, anyhow - a maintain aspect ratio option would be an incredibly useful time-saver.