Re: Has there been a paradigm shift and nobody told me?
In Linux at least you have that choice. Install Mint and run MATE or Cinnamon, uninstall Zeitgeist or whatever. It's your call. Pretty sure you can turn off indexing in WinX as well.
So let's say I want to launch a video editing app, something I do reasonably often but not often enough I have a dock shortcut (although frankly I've stopped making those because I never use them). My choice for video editing is KDenlive, and I use it fairly regularly. I can click a menu-opening button, navigate through one, maybe two levels of menu and click a thing (just checked, four clicks). Or, I can press a button, type 'K' and hit enter. I think the first time I launched it I had to type KDen, but Gnome has learned what I mean now and I don't have lots of apps whose names start with K.
In either case I have to know what the app is called, or at least recognise it's icon. Although in the second case I could just type "video editor" and still get the same result.
However, I can also type "video editor", hit tab and launch a google or wikipedia search for that term. Sure, I probably already have a browser open, but I might not. Same number of steps though, but it's all through one interface. My computer is not a web page, but web pages represent a lot of what I do with my computer and being able to hook into them painlessly is nice. It's not essential, at all, but neither is a lot of stuff we like to do.
A slightly better example is Stellarium, which I use a lot. That's Win-S-Enter now, but it can also be "planetarium" (it shows it's link alone after 'plane' on my machine). But where would I look for that in a category? Science? Graphics? The (n)ever-useful "Accessories" category? Then there are apps which create their own app categories. Thanks "Limbo", you really needed to make a top-level menu entry? Nested, categorical menus need sorting by hand. Search-based, learning interfaces don't - they sort and manage themselves based on use levels.
Just to be clear I use Gnome Shell, not Unity. I am a huge fan of how slick, easy and seamless it is compared to the old 2.x/Win95 UI style. I'm not in any way saying search-based UIs are better for everyone, but they are better for some people. They do very well in "normal" user testing, which is why they're appearing more and more - techies seem to like them less though. I have speculated about the reasons for this in the past on this very website.