In the eternal wheel of repetition in IT, we're nearing a complexity peak / inner product effect for D.E. that looks just like the peak I experienced of "doing everything in emacs" around 1990. Modern vim, and other editors, don't really look much like 1990s era emacs.
People will make jokes in the future about current D.E being useful for everything except being a desktop environment, just like the well known jokes about emacs being a great OS, but only so so text editor.
The next rotation of the same wheel will probably be "doing everything in web browser"
currently I mostly use the "vim" of desktops rather than an "emacs" of desktops, I switched from awesome to xmonad a year or two ago, don't remember why.
I have some mythtv front ends that use ratpoison as a WM because at least in the olden days mythtv wouldn't run even in fullscreen unless it was on top of something providing window management, weirdly enough.
I use a DE for the same reason I use vi mode in emacs; I have the resources to do it, and there's a bunch of features that I'll probably only use a few times a year, but it's nice to have them there.
I also switched from Arch to Ubuntu because I decided that the control I was losing was worth it to reduce the number of things I had to keep track of.
The beauty of free software is that it's not like one paradigm is being forced down our throats, we can pick and choose. I hope KDE does well for the same reason I hope icewm does well, because more users of free software is a good thing.
There is always a cognitive load and time cost to a feature. Even if you don't use it.
andmarios had a good point, innovation is defined as linking your phone to your desktop such that the audio out mixer volume crashes down when you get an incoming phone call on the cellphone. That's quite a cognitive load to learn about, set up, test, inevitably debug. If my wife's using my desktop and I get a call 100 feet away, what happens? She gets to debug why her phone doesn't connect to her account. It seems the "best" UI is just a physical volume control dial on a discrete amp connected to speakers, which is what I actually have. Its much more convenient than a software volume control.
Also most of the "features" tend toward lowest common denominator, not universal. So a super duper copy/paste system that works DE-wide works great with things you never cut and paste in, like perhaps the GUI FAX config screen. However it doesn't talk to emacs and vi where I actually do almost all my cut and paste (or does it connect... I'll be impressed if it does, I wonder how much work it is to set up and inevitably debug) In a similar way if I get a legacy voice phone call the DE might mute my music, but is it smart enough to do so for a google hangout video chat incoming, or a legacy skype, or a hangout on my tablet not my phone...
I would tend to agree, if they like it, good luck to them, although I'd never voluntarily use that kind of thing for productivity and style reasons. Just not conceptually appealing.
People will make jokes in the future about current D.E being useful for everything except being a desktop environment, just like the well known jokes about emacs being a great OS, but only so so text editor.
The next rotation of the same wheel will probably be "doing everything in web browser"
currently I mostly use the "vim" of desktops rather than an "emacs" of desktops, I switched from awesome to xmonad a year or two ago, don't remember why.
I have some mythtv front ends that use ratpoison as a WM because at least in the olden days mythtv wouldn't run even in fullscreen unless it was on top of something providing window management, weirdly enough.