It's not the most frequent method for launching. According to MS, their metrics indicate pinned task bar items are, or are trending to be, the most frequent method.
When I don't remember the name of the thing I want to launch (which is quite frequent), I rely mostly on positional navigation through a customized start menu. That is, I don't remember programs by name, I remember them by where I left them. Windows Vista / 7's start menu was a major regression for my use case (the scrollable treeview with expandable items destroyed absolute screen positioning); I had to replace it with Classic Shell to get usability back.
For most people the "All Programs" menu quickly turns into a circus. Curating it is a chore.
They are messing this up in Windows 8, as every time you install a application, including desktop applications, all of its start menu items get pinned onto the start screen. I'm afraid most users will never bother to unpin them.
I used to curate the All Programs menu. What that did was mess up uninstallers, because they could no longer find shortcuts to delete them, so I ended up with lots of dead shortcuts that needed clearing out.
So now, I create a bunch of category folders (Work, Development, Entertainment, you get the idea) in the Start Menu profile folder (rather than the Start Menu\Programs folder), and copy the handful of app and applet shortcuts that I actually need in. I leave the All Programs menu to fester and ignore it. With Classic Shell, this works well; the classic start menu, in XP mode, shows my folders as top-level expanding menu items.
Windows 8 start screen right now has a sideways scrollbar scrolled by the mousewheel! It's a sad joke. But I'm sure that aspect will be cleaned up somewhat before release.
I'm not looking forward to Windows 8 because it's a mess; it jams together two completely different idioms, tablet-oriented full-screen apps with legacy desktop apps. But as it is with Windows 7, I don't run any - none at all - applications maximized, not even VNC or RDP connections. I have a minimum of 5 windows open at all times across multiple monitors, in a cascaded configuration for quick access. The idea that a maximum of two apps with a fixed split position is workable? Only for tablets and, maybe, laptops. The full-screen idiom is a complete non-starter.
So I'll be spending most of my time in Windows 8 in the legacy desktop. I don't think it would be a big development hardship to have a floating start menu emulator in the lower left corner to avoid doing a big dramatic transition to a full-screen menu just for launching an app. So I'm not too concerned about my personal productivity.
But I am concerned for MS. I don't think Windows 8 is going to work. It's a classic power-play; trying to leverage an existing monopoly to invade a new market. By forcing a tablet UI on all desktop users despite their protests, MS hopes to prime the market somehow for their tablet (Surface etc.) offering. But I think it's a step too far; I don't think they have the leverage they think they have. They certainly have built up contempt for their users to try and pull it off, though.
(Have you tried the preview in a VM? It's shockingly bad for something allegedly going to run on people's desktops. The discoverability of the Metro UI is abysmal. I was in the IE browser, it took me a good 5 minutes to figure out how to enter a URL, because "helpfully" everything was hidden. It was complete desperation that I right-clicked!)
It's certainly not the most common method; I'm sure point-and-click is. But the kind of people who use keyboard launchers, the ones who are sounding off the loudest on their tech blogs and sites like HN and Reddit, surprise me. I'm sure the average user might be confused, but for me at least, I'll do what I do with Win7, OSX, or Ubuntu: Super + typing + Enter.
When I don't remember the name of the thing I want to launch (which is quite frequent), I rely mostly on positional navigation through a customized start menu. That is, I don't remember programs by name, I remember them by where I left them. Windows Vista / 7's start menu was a major regression for my use case (the scrollable treeview with expandable items destroyed absolute screen positioning); I had to replace it with Classic Shell to get usability back.