As a long time Linux user, this comment makes me sad since many of those features were copied from Linux (many from Unity) :)

Unity really was a great project.

KDE 6.6 is great to me, but there are some quirks I have found. Their "peek at desktop" feature is annoying, I want "minimize all" but you have to do some scripting to enable that.

I've noticed that clicking the network button to see wifi status shows traffic rate, and that seems to lag and I suspect it has an impact on throughput.

I'm interested in Cosmic when it matures some more.

I think most of its features predate unity (compiz was integrated but existed before)

I don't think all the same shortcuts exist out of the box, although win-drag/win-right-drag to move and resize windows (might be alt by default) is _so_ much more convenient than the usual border/title dragging that you might find you don't miss them.

My personal PCs have enough screens that I haven't tried. Though I do really like Windows snapping features on my work laptop (can't change OS there).

I haven't played with other windowing systems to judge too much. And just picked right from screen shots/gifs to not need to try.