View Unredered Video in Final Cut Pro

I'm making my way through Larry Jordan's amazing new book, Edit Well: Final Cut Studio Techniques from the Pros and came across a real gem.

In FCP a red across the top of the timeline indicates that files must be rendered in order to see them during playback. Using the keystroke option-p, however, allows you to plow right through. This is a great way to see if effects are timed correctly before actually committing to rendering.