I don't know just how many people did Unity successfully prevent from switching to Linux!
With regards to usability and customizability, IMHO Unity seems to get worse with each release, so eg. now it no longer supports screenlets, and even the "Unity Tweak tool" no longer seems to work for several useful "tweaks".
But, I just don't get why do people assume it's either "plain" Unity or back to Windows. Have you ever tried Kubuntu? Or MATE, Cinnamon, Xfce flavours? I personally find KDE Plasma 5 the best DE ever, period - that is, once you invest those few minutes customizing it / fixing its few oddities here and there. Why don't you try it out?
For me, my biggest beef with Unity was a death from a thousand papercuts. EG: i wanted to open a file in a program and had to navigate to the location, and couldn't just copy the folder path as I did on Windows. Or when I wanted to Alt-Tab between two windows of the same program, I couldn't do it with Alt-Tab. To remove it, the forums told me to launch a program which then for some reason didn't open when I double clicked on it. And then I realized that Sublime Text was not longer called Sublime Text but Ubuntu somehow renamed it to the last file opened as admin, which was aparently a well known bug with Unity.
Then I read that the next version of Unity is a rewrite from scratch, with usually means many new fun bugs, and just said 'forget it'.
Now, is any of these DE simple to use and with well-thought defaults? I can try out a few ones (after all I will do a clean wipe of my desktop) but sadly don't have the time to test more than a few DEs.
I think KDE, MATE, Xfce and Cinnamon have all (mostly) sane defaults, and are simple enough to use, so it's mostly a matter of personal preference. I'd choose KDE though - I have used Xfce for years before, and it always felt somewhat limited.
With regards to usability and customizability, IMHO Unity seems to get worse with each release, so eg. now it no longer supports screenlets, and even the "Unity Tweak tool" no longer seems to work for several useful "tweaks".
But, I just don't get why do people assume it's either "plain" Unity or back to Windows. Have you ever tried Kubuntu? Or MATE, Cinnamon, Xfce flavours? I personally find KDE Plasma 5 the best DE ever, period - that is, once you invest those few minutes customizing it / fixing its few oddities here and there. Why don't you try it out?