All considered, I'm happy with 16.04 and I'm staying here at
least until 18.04.
However, many packages aren't updated in the LTS releases which prompt one to move over to the intermediate releases. I wish Canonical were more agile about updating compilers and such on LTS versions.
You can find a PPA (apt repository) for almost any app or tool these days. I find that just adding a few of these for specific cases to a LTS release gives you the best of both worlds.
My current ones: git, Google chrome, flux, node, nylas, spotify, tarsnap, blender
I was referring mainly to compilers and system libraries; stuff like gcc, glibc, ...
I went from 12.04 to 16.04. I skipped 14.04 because of the DE which I couldn't bend to my will. I remember that I had similar problems in the last months on 12.04, with some new versions of some programs unavailable on 12.04. I guess that I could have installed them in a 14.04 docker container (would the kernel version have been ok?) Maybe you can do the same for a compiler. I don't know if it would be convenient. I'm more into scripting languages and I use gcc directly only every other year or more, so no big deal for me.
I agree with not needing Unity. I'm on Gnome flashback and 16.04 finally let me get about the same DE I had with 10.04. It's Gnome 3 but it looks like the Gnome 2 desktop, with only one panel to the bottom and the compiz cube. I use the 3D rotation effect to remember which side I came from. A 2D slide doesn't hint me enough and I get lost in the virtual desktops. I don't use the cube for anything else. All considered, I'm happy with 16.04 and I'm staying here at least until 18.04.