I gave up on Ubuntu when I could no longer have faith that my environment would be recognisable from one release to the next. For me, and my mother, that's a very important part of "just works".
You caught Ubuntu (or Fedora or other distributions that moved to GNOME 3) were on GNOME 2 greater part of the last decade. A breaking UI change had to be done at some point, and it happened to be 2 years ago. Even on macs, there was a huge overhaul going from OS9 to OSX in 2001.
You can make a point saying that you don't like the new UI. That will be a much more sound argument than saying the environment is changing from one release to the next.
My mother started off on 8.04 LTS. When upgrading to 10.04 LTS the window buttons changed sides and there was a new theme (this is enough to throw many users). When upgrading to 12.04 LTS there was a change from Gnome to Unity.
My mother now chooses to use a Mac because she was fed up with her computer "changing" each time I updated it. I doubt I could convince her to try any Linux distribution again - there are no perceivable benefits for her.
Edited to add: Not that I think Window Maker is necessarily the solution. I'm just pointing out that the default Ubuntu repos contain a huge number of window managers and even a few desktop environments which haven't changed that much between releases.