Our usability team is conducting usability tests of the Notes 8 shipping product. One of the issues they've uncovered is that many users do not notice the "snap" control (the little arrow) so that they can snap the preview closed (or snap the sidebar closed.). The problem is shown in the following picture.
So we are trying to make it more visible without using up any more screen real estate. We have several ideas, and Sheri Branco is going to be running some quick tests in the next week.
Here are three of the options we'll be testing. Which one is the most noticeable without drawing any undue attention to it?
Added gray around the arrows (which will change to orange on hover, just like in Notes 8)
... I'd tell you which one I think will work best, but in this case, it's Sheri's test results that really matter.