I find myself thinking about the historical criticism that has been aimed at the Linux ecosystem, that it lacks design awareness and doesn't have a unified aesthetic principle..
Then I see something like this and I wonder if in a way that wasn't a strength.
I mean "brand coherence"? I can't imagine what that has to do with Linux. Everything has always been so configurable, that in a way a lot of aesthetic decisions were left to the user and the app developer. People used Gnome 2, and other desktop environments to design their own desktop.
I used Gnome 3 for a few months last year when I was making my swing back to using Linux full time with Fedora. I found it usable enough, but it's lack of configuration options became frustrating because it didn't allow me to fine tune my GUI workflow, it also handled multiple monitors terribly and being unconfigurable didn't allow me to adjust that.
I was initially excited about Gnome 3 but it was pretty shallow. KDE 4 is an amazing desktop environment, with lots of configurability and in keeping with letting the user design their own experience. I made a good long stop there, for about a year, optimized my windowing workflow (one size simply does not fit all) then ended using xmonad but running some KDE apps..
It looks like GNOME and Unity are turning against the traditional spirit of the Linux community. I don't think that's for the better. The answer now to the question "I don't like it." for these Desktop Environments is "If you don't like it, tough." where as before it was "If you don't like it, change it."
I don't think Linux devs should ape Apple, Google, or Microsoft. Linux can be, and is, for everyone.. but it's especially for hackers and for people who like to tweak their experience. A project like a DE is huge and by turning away from hackers they're going to limit their ability to pick up new devs and devs are going to turn away from the GTK.
For some people Ubuntu IS Linux, Gnome IS Linux.. but for others not so much.
I don't develop desktop applications currently but I would like to. I don't see myself wanting to start a new project or get intimately involved with one that is dependent on the GTK at this point though.
Fine tune? It doesn't even coarse tune. I'm using gnome 3 at the moment and it allows me to set my preferred media player as VLC over the default Totem... but it won't bother using that setting and cranks up Totem every time.
Also, rather humorously, the 'preferred applications' part is hidden behind System Settings > System Details > Default Applications. News to the Gnome folks: user app preferences are "Personal" not "System" (using their own terminology). Unless, of course, my selection here changes all users' settings... which would be equally insane.