No idea about Ubuntu, but I installed Centos+GNOME over the summer, and frankly I didn't think Linux desktop had moved on much from 7 years ago when I last tried it. I have to say that I was expecting something better, and I was disappointed - because I really wanted it to be better than what it was.Windows has always driven me up the wall, so that's not an option here.
The question of Mac versus Ubuntu MATE has been much on my mind recently, though. I feel like the Mac user interface has been in decline for a while now, and the OS has been getting gradually more cranky and counter-intuitive and unhelpful. At the same time the Linux world has continued to improve, and it's at the point now where I find that I prefer Ubuntu MATE in many respects. Also, Apple's hardware lineup has left me befuddled and frustrated for a while now. (Which is why I'm still running a Mac Pro from 2009.)
Aperture was one program that kept me tied to Mac OS, since it didn't run on any other system. Then Apple abandoned Aperture, and I moved to Adobe Lightroom. And it was good, but it doesn't run on Linux. Now Adobe are going subscription-only with Lightroom, so that's the end of that (for me at least). Now I have to start looking once again for photo management-and-editing software.
This time it's going to be something that runs on both Mac and Linux. And I'm quickly running out of programs that "hold" me on Mac OS, so the possibility that my next system may be Ubuntu-based looks more and more plausible.
So after all these years, I could not use GNOME outside it's server function that it was bought for. Although applications like Firefox and Thunderbird are great, they are still this strange Linux mess that's the same as it ever was. Extremely functional, but lacking the polish that you see in OSX.