For most people, what are the easiest ways to control something? Clue: it's not by typing words out, letter by letter, and nor is it by moving something around on a tabletop.
Apple has Siri, Google has Voice Actions for Android, and other stuff for Search. Amazon recently acquired Yap for their voice recognition software.
Voice is not great yet, and it is after all stunningly complicated. Leaving aside that accents vary the sound of the human voice a great deal, vocal communication is a beautifully subtle human art. More so than with the written word, it depends on context, intonation and inflection, and any face-to-face vocal exchange is generally augmented by all sorts of gestures and facial expressions. Wow, you wouldn't want to be the computer that has to reduce all that lot to noughts and ones.
It's not only difficult for computers though. It's hard for us fleshies too. We're not used to stripping all the good stuff out of the way we speak and reducing it down to commands.
We might hate to admit this, but we're all computer programmers these days, sort of. "Start my application." "Quit it." "Make a calendar appointment." "Delete something." Techie types are totally used to communicating like that when they're pressing buttons on a computer keyboard, but even they find it awkward to be so purist when speaking. It almost feels like a bad habit to get into: being so expressionless.
Also, voice is all about immediacy and flow. How comfortable do you feel when someone pauses for 10 seconds before responding to even your most basic comment. Bit of an idiot, no? That's what it feels like talking to a computer, which has to upload your voice to the Internet, where it gets processed and returned as something more usable.
Siri has captured the imagination precisely because it's the most natural voice control we've seen so far. All those amusingly human exchanges http://www.sirihumor.net/ with Siri are exactly what makes Siri feel usable. Sure it's very clever and capable too, but throw in a few funnies and it's far more reassuringly human.
However, it's still a bit like ordering your half deaf Grandmother to do your domestic chores for you. Perhaps not your proudest moment. Especially in public.
What I love is that touch is getting increasingly gestural and expressive. Inertial scrolling is the most obvious example. You fling your content around, and it behaves like it's been flung. Very reassuring. We live in a physical environment - and the more accurately our digital systems reflect behaviours that we're used to, the better.
I'm sure there's a long way for touch to go too. Touch keyboards are generally unsatisfying, partly because haptic feedback is so poor. (Haptic feedback is when something gives you tactile feedback which helps confirm that you've done it. A physical button that presses down with a satisfying click for instance.)
Also, does touch make you feel clumsy? Great big sausage fingers getting in the way of the screen or accidentally pressing the Backspace button when you meant to press "M"? Any time computers screw up, or the UX is poorly thought through, we blame ourselves. That's not a good experience.
I wonder if reverse-mounted multi-touch screens will help? The PS Vita looks like it'll be the test case.
Digital experiences that suit human beings
It strikes me that all of this is part of the same movement. Digital device form factors, and their software, are integrating more and more tightly with the needs and natures of the human body.
This is simply because people can fit decent technology into almost anything now. As a result, we're no longer devising crazy ugly machines just because we can.
Usability is the absolute key to the success of modern hardware or software. That's all there is to it. There is greater opportunity for this than ever before.
This is also proof that usability is becoming more subtle than ever before. In the case of either hardware or software, the tiniest flaw can knock an entire experience askew, and it may well be harder than ever before to identify that flaw. We users become more exacting as the computers become more capable.
We are getting ever closer to parity between devices and their use cases. It's a very welcome advance, but it makes users more critical than ever before, and it makes designing successful software or hardware even more demanding than ever before.