I don't know that anyone has ever held a "theory that our brain 'sounds out' words each time we see them".

From what I've seen in articles, videos, etc.:

Mac OS X Lion gets almost everything right, but there have always been little things in MacOS that annoy me to no end when I try to use it. If it was free software, I would have switched.

Windows 8 . . . I haven't noticed anything compelling. Probably fine for most people.

Unity is the only free software desktop that puts the menu bar in the right place by default. The indicators seem to be shaping up well.

Gnome 3 has the potential to be awesome, I think, because they are exploiting JavaScript for so much. That Linux Mint will be releasing extensions to make Gnome 3 like Gnome 2 is a testament to this. Show me that the menu bar can be put in the right place and I'll consider it. Put it there by default and I'll probably switch from Unity.

KDE Plasma looks like it has good widget, window, and file management, but I've only seen screenshots and may be imagining things work a certain way.

Offer compelling value?

Suppose you get past the hurdles of hardware compatibility and installation, and suppose you have perfect work-alikes of any program for Windows or Mac, what then is the reason to switch? Most people still don't understand the importance of free software, so that's a non-starter. (I still have to say "free as in speech, not as in beer" or something like that, and I still get blank looks.) Forget about freedom then for most users MacOS X has everything Linux has and more. As far as I can tell, Windows is unfriendly unless you use some whizbang IDE, but even then I've been able to kluge around some problems at work with a bit of ECMAScript (ActionScript, or whatever they call it).

It seems there are now 5 major threads of desktop environment development: GNOME 2, Gnome 3, Unity, KDE 3.x, KDE 4. There are plenty of others with less momentum like E, ROX, and LXDE. Well, maybe now E has more than G2 and K3. Only one of these (AFAIK) has made the crucial step of having a single menu bar on the screen. (Yeah, I'm not going to justify that in this space.) That's Unity, which is still using Nautilus. Some "upgrades" ago, Nautilus starting dropping features, and before that the default layout went from spatial to browser. It is fast becoming unpleasantly useless, mostly because everyone is focused on the latest "shell" idea and making everything a copy of what they see on smartphones and tablets. Sorry, I need to use my computer to work and turning it into a media center is not helping me do that. Yes, I can do things the old fashioned way—well, mostly—but then why do I need Linux? I can do those things on Windows (cygwin) or MacOS X (it's Unix).

Linux desktop environments are doing nothing new, or even old, that gives people a compelling reason to switch. Even if they did, you'd have to demonstrate that value and get people over the learning curve. People are too busy with other things. It's hard enough to get them to do things a better way even when their jobs are on the line.

I really don't like Mac. Never mind the feeling dirty when I use it; there are things about the interface, which is mostly excellent, that are just wrong for me. And yet every month it seems more likely my next computer will be a Mac. The dirty wrongness of it might be more bearable than the OMGWHYWHYWHYSOBSOBSOB of Linux.

(Sleepy and getting over a cold or something. Hope I didn't accidentally summon an elder god during the microsleep.)

This seems to me to be a grievous mistake.

Yes, it should be able to. There's a lot of stuff the graphical shell should make easy, but those we have are going in other directions.

Whatever doesn't kill me makes me stronger . . .

. . . unless it maims me.

The maiming sucks. I'd rather avoid it.

Yes. Especially then. It builds character.

A way to turn it off and go outside to play.

Amigans agree:

http://en.wikipedia.org/wiki/Magic_User_Interface