The general point was that "Improvement" that ruin muscle memory usually aren't. It should be the most basic UI design principle.
One should be able to instinctively click on the Gmail icon while focused on the task at hand. If the icon isn't where one expects it to be you are no longer doing email things. Same goes for having the user search for the inbox inside the application. If they can't find it they are unproductive and feel dumb but they aren't to blame. Some bad designer came up with the brilliant idea to call it "all mail". The inbox is expected to live at the top of the menu. You can't improve it.
It's such basic stuff. It's like someone used your tools or your kitchen and put everything in a new spot. Eh, I mean the wrong spot.
I could give 1000 example inside windows but it seems everyone is trolling their users. They all want to create the new and improved slashdot, now without threaded discussions! - Hurray!