I just learned a sweet little UI tweak in the latest Aperture update. As you already know, when you're working in Quick Preview mode, you can't do any image editing. Sometimes people forget they're in Quick Preview, try to edit, then remember where they are. The solution was always to hit the "P" key to exit Quick Preview.

That still works, but now you can hit any of the Toolbar buttons, such as Crop or Straighten, and Aperture 2.1.1 will take you out of Quick Preview mode and enable the edit command. Just a nice little adjustment to save you a keystroke.