I'm glad to know this, since I don't really like the new interface. Not yet, anyway. They may have gone overboard in trying to simplify things. 1. The default theme is a bit too bland. (I feel like I may as well be viewing it on a black-and-white monitor!). 2. The HD themes are nice, but they can overpower one's viewing of the message list. I like a nice background, but I don't want distractions. 3. The formatting bar on the compose screen has no color ! I count on color to help me 'see' the buttons (text color, text highlighting, insert images, etc.) These are all aesthetic complaints, granted. But for now, I'll stick with the old interface.
My monitor (a 17" Acer, NOT widescreen) doesn't even 'register' any difference between the display settings ! (Gmail said that might happen for some.)
Also, your example above reminded me: I also don't like the icon-only approach to the various functions, esp. with them all being basic gray. Old Gmail has text buttons ("delete," "archive," etc.) which I prefer.