I think it's a nice idea, but it isn't implemented well. I just played with it for a few minutes and, several times, it didn't re-hide the "distractions" when I went back to the edit box. When it does that (i.e. when it continues to show the sidebars while I am in DFW), I have to click the DFW button to turn it off because WP thinks I am still in DFW view, then turn it back on again. It has done this (not re-hiding things) easily 40% of the time.