I discovered the new "sneak preview" function of the editor. This is a nice idea, but I think the way the preview is updated is not optimal. If I understand this correctly, the preview is updated if the edit control loses the focus. Also, some extended functions of the editor seem to trigger the update as well. At least I get some updates when I don't expect them.
I would prefer a solution that is based on the idle time of the user, if this is possible. If the user is inactive for a certain time and he did some changes, the update is triggered. Since I assume that the preview includes a round trip to the server, I would adjust the wait time dynamically. I would measure the round trip and display time of the last update and would set the wait time as a multiple of it. In addition to that, I would add an explicit update button and/or keyboard shortcut to initiate the update.