It’s even worse for first-time users: There’s no visual cue at all for returning to the Metro interface.
This mattered two decades ago. It does not matter now. Two decades ago, there was a large number of people who were just starting to integrate computers into their daily lives. This is no longer true. Computers are integrated into people's daily lives. The only people [1] who are "just starting" to integrate computers into their daily lives are the same people who are "just starting" to integrate using a toilet into their daily lives.
From now on, people will grow up with computers, and I think we should design interfaces to reflect that. "But what about first-time users?" should no longer be an interesting question.
[1] I'm sure someone can come up with specific counter-examples. I submit that those cases are rare enough that they shouldn't be a primary consideration for designing interfaces. Of course, there should be interface back-doors for disabilities and such, but that is not the same as primary considerations for most people.
It's not about new to computers, it's about new to your interface.
If you have a new interface, especially one that works differently from the old interface in a notable way, you can't assume that everyone will instantly figure out your new interface without cues.
I think it would be quite unlikely that the majority of users would be given a Windows 8 machine without some kind of tutorial. Windows has had a "Welcome to Windows" since at least Windows 95 (IIRC). Corporate users are generally given a brief documentation page on how to use their computer (we rolled out Windows 7 last summer with a 3-page document with screenshots of how to get around).
There will be precious few who can never get the hang of it.
Even if there are no first-time users anymore, I think computing in general can benefit from User Interfaces being developed as if they are developed for first-time users, and the advanced options layered underneath. This is where OS X gets things right.
In addition, computers may be integrated into daily lives, but I think this definitely does not mean the opposite - that people have learned how to operate them properly, despite them being so integrated. If level of integration into society means that user interface does not need to cater to beginning users, there would be no designers left to make designs - only engineers (perish the thought :) But seriously -- and forgive me for using a car analogy -- but the basic operation of a car is actually simpler, rather than more complicated.
To be fair, some OS X advanced options are in hair-pulling places, which I believe only underlines how hard it is to market computers to the masses with differing layers of knowledge
This mattered two decades ago. It does not matter now. Two decades ago, there was a large number of people who were just starting to integrate computers into their daily lives. This is no longer true. Computers are integrated into people's daily lives. The only people [1] who are "just starting" to integrate computers into their daily lives are the same people who are "just starting" to integrate using a toilet into their daily lives.
From now on, people will grow up with computers, and I think we should design interfaces to reflect that. "But what about first-time users?" should no longer be an interesting question.
[1] I'm sure someone can come up with specific counter-examples. I submit that those cases are rare enough that they shouldn't be a primary consideration for designing interfaces. Of course, there should be interface back-doors for disabilities and such, but that is not the same as primary considerations for most people.