I keep my Render Queue panel in the same frame as my compositions — that way when I hit render all I see is the progress of the queue. I think I'm getting the same speed boost as CapsLock without the ALL CAPS SCREAMING.
If AE doesn't have to blit the screen each frame, I think you get the speed up either way — but I don't remember the last time (or version) that I tested out the theory. Now I have something to do while eating lunch at my desk tomorrow.
Somebody ran some tests on this a while back, eg comp window foremost, comp window behind, comp window closed, caps lock on or off etc. Can't recall the results though. I also have render queue docked with comp window.
And yes, I was also thinking recently that it's starting to seem a bit antiquated.