I've had some thoughts on this recently, and wholeheartedly disagree. We spend aeons engineering stability into every other interface within a software ecosystem, since it's supposed to improve stability, reduce surprising breakage, improve engineer efficiency, discoverability, etc., but when it comes to interfaces in the user plane, it's like the only established methodology is FUCK YOU Driven Development.
In these systems, and Gmail, the user is not considered an intelligent, complex actor in the system, but instead something more like a child sitting in a cinema whose only criteria for synchrony is to be repeatedly dazzled by confounding changes to the way it interacts with the system.
This is fundamentally wrong in so many ways. Not least, the user is the main purpose for the existence of these systems (er, right??), and yet the user's interface to the system is the one most likely to functionally break without warning.
You cannot address the reliability of the entire system without considering the last mile - dropping a change the size of the Gmail redesign on millions of users without a multitude of small iterations, or with a huge amount of fanfare and warning, is an unmitigated disaster for the reliability and efficiency of the overall system.
I don't give 2 fucks how much of the scientific method was abused to create the new system up to that point, if it doesn't comfortably fit the millions of delicate tendrils that have grown between my mind and it, then from the user's perspective the change is much closer to an abject failure.
I suspect in years to come this will be an increasingly important area for study, and I pray the outcome to some extent will simply be that corporations will need to give up achieving quick feel-good wins by arbitrarily fucking with the user-machine interface, although I could be wrong. We could always be further reduced to that mindless entertainment-only child in the cinema, responsible only for the most basic direction of the outcomes of our interaction with the overall system, the tacit attitude of the large corporations as they drop huge changes like this without warning.
The outcry we hear over these changes isn't just bored people being picky, it's the sound of a trillion dying neurons in a million interconnected biological systems. Much as a fully grown cat wouldn't fare well being stuffed into a jar, the users here suffer just the same. Thin the cat's diet slowly over time, widen a border here, replace some text with an icon there, and the small bits of death and shrinkage that occur over time will mean that cat will soon be ready to contentedly purr its way into that jar and fall into a dreamy slumber all of its own accord.