A few weeks ago I had to dig up an old 12.04 machine and bring it back to the modern age. Much to my surprise, I was able to upgrade it all the way to 15.10 with minimal hassle. While the normal apt repos were dead for 12.04, Canonical keeps around an archived mirror. So you just edit the sources file to point at the archive, and then you can upgrade from there. Impressive.
Not that Canonical/Ubuntu don't have their warts. The Amazon fiasco, Unity, their cloud services, etc. And at the end of the day it's still Linux, with all the problems that brings. But, all things considered, I rate Ubuntu as the best of the bunch and feel grateful for the gift they give to the community.