In my experience, Apple products offer superior technical value. Compare the touchpad in a MacBook to one of the knock-offs. OSX has better graphics performance and more software available than Linux. The build quality of the Apple products is higher. Point being, there are objective reasons and tangible value that make the MacBook worth its higher cost.
Same thing with the car example.
I'm still not convinced that Facebook is gaining any tangible value from such minor aesthetic changes. Are there any real numbers to back up the claims that real users care about such things?
"Here's what the left-brainers have to think about such a well though-out and through design process..."
It's hinging on the effort that went into the process, which is by all means extensive and impressive. Its' defensive. But I think your line of questioning is extremely important and I'm a designer, so I'll give it a bash with explaining why they did this.
I don't think you could ever back up with numbers that these changes 'matter' to users. Any research that could be done would, in the words of someone better than I – be used like a drunk uses a lamp post. For support, not illumination.
At the end of the day, I'm inclined to agree that these changes are negligible for users. What this is more a case of is Facebook deciding they care about the craft and quality of the visual design in their product. Regardless of if users give a toss. The change isn't quantifiable in numbers. It will most likely not change the bottom line of the company.
But what it does do, is communicate that Facebook cares about visual design craft. This is part of branding. Deciding they care about these things, to have the image of the company they want.
These changes are on par with Apple choosing to make a glass staircase in their stores. It's like Twitter choosing the colour of their office furniture, it's like any other company implementing anything that does not directly or clearly affect returns or is quantifiable in numbers. Simply put, it's a culture thing. They've decided they care about visual design craft and so they put money into it so they can have high quality visual design craft. And they have done that here – this is high quality.
Apple offers a fantastic tactile experience and OS X -- the user experience ecosystem is the big sell for them, which is why their operating system has been a loss-leader for so long. A similarly priced Dell XPS 13" is going to out-perform a new MacBook pretty much everywhere but battery life (which it misses by something like an hour), but the Apple is the more attractive buy because of OS X and the joy of using it.
It's demonstrated and acknowledged, through profit and market dominance industry-wide, that there's more to life than tech specs, and that more is user experience. There's really little else to say on it...
All of those "trivial changes" combine to give users the perception of completeness, cohesiveness and value.
When broken down into exacting detail, it's easy to dismiss them as imperceptible; by themselves, they mostly are. But the cumulative effect of these decisions leads to the perception of a better product.
Compare and contrast a MacBook Air with any one of the cheaper knock-offs. They may pretty much look the same, but the Apple product has an intangible sense of being worth more.
The same thing goes with cars—sure, they all have the same basic design, but put an Audi next to a Lada and you can immediately tell by looking at them which one's worth more.
That's the value of visual design.