Touch UI is not the future of everything.
Apple beat even the most optimistic expectations and sold over 15 million iPads in the first year of its release, and it looks like the second version is just around the corner. The competitors are lining up as well: the Motorola Xoom, running Android 3.0 Honeycomb, the HP PalmPad, and the RIM Playbook all look like interesting offerings.[^1]
Many have pointed out the sad irony of the fact that Microsoft, who has been pushing tablet PCs for over a decade, seems to have by far the least compelling offering, and no apparent serious road map for future products that address the deficiencies of desktop Windows on a tablet form factor. Historically, Microsoft's tablet and even smartphone operating systems have been desktop Windows pared down (and barely, in the case of tablets) for use with a stylus. I had a convertible laptop, in fact, and though I was excited about the idea, it never really worked that well, for reasons I was never able to articulate.
In the aftermath of iOS, the reasons are pretty obvious.
There were many aspects of the iPhone that revolutionized and redefined the smartphone market. The iTunes and iPod ecosystem certainly helped. So did apps (though third party apps didn't come until later, so didn't really contribute to the initial popularity), and so did Apple's traditional focus on hardware design. But the single largest and most revolutionary factor of the iPhone's (and the iPod Touch's as well as the iPad's) success was the user interface. Apple designed the UI around a new paradigm of touch and direct manipulation, shining a light on how elegantly simple, refreshing, and intuitive human-computer interaction could be. The dominant paradigm shifted and now the measure of a smartphone UI basically boils down to how well the paradigm is executed.[^2]
Apple's touch interface allowed the dismissal of many of the abstractions that people found difficult about computing: Buttons took a step away from metaphor and toward the physical as did navigation and scrolling. Diminishing these abstraction-distances made the idea of transforming the device into the specific running application more feasible and more emotionally satisfying.
While it makes complete and and perfect sense to collapse the distinction between input/control and display for a mobile device like a smartphone because by their nature these devices are constrained by their form, I would argue that it makes less sense as the device gets larger. Larger devices (including, arguably, current iPad-sized tablets) are fatiguing to use for long periods of time, heavy to hold up and ergonomically unsound. Occlusion can also be a problem.[^3] As this UI concept video demonstrates, these problems get bigger with the device. On a real workstation, these problems become intractable.
With OS X 10.7 Lion, Apple wants to bring many of the things that make iOS appealing to the desktop. For certain aspects, this is great: saving application/document states, abstraction of the file system, simplification of application management, etc. For other aspects, the results are ambiguous: disappearing scroll bars and reversing the direction of two-finger scrolling, for example. To take the latter example, Apple is attempting to bring desktop multitouch gestures closer to the iOS counterparts. In 10.6 dragging two fingers down on the trackpad scrolls down a page. In 10.7, the same gesture scrolls up, just as would happen if you were to touch an iPhone's screen and drag down. There isn't necessarily a correct way to do this (it reminds me of the change of the default in mouse-look direction in first person shooters), but it's weird to change an established convention in a way that's not really any more intuitive. The intractable problem here is that a direct manipulation paradigm is fundamentally different from an indirect one, and trying to force one onto the other creates a bad experience.
Still other paradigms Apple is trying to bring from iOS to the desktop are just bad. Full screen applications, for example, are perfectly sensible on a handheld, size-constrained device (and maybe even on smaller laptops), but on a world of large desktop screens, it only restricts the interface artificially. It's also really strange to see Apple embrace this concept now when it makes the least sense after so many of years of denying it completely.
Just as Microsoft tried to force the desktop's indirect manipulation UI paradigm onto devices where a direct manipulation UI would have been more appropriate, and suffered for it, Apple seems to be trying to do the exact opposite. There's no denying that Apple is the uncontested thought-leader in computer UI, which is why I'd be much more interested in seeing them offer new ideas in desktop UI with the very different inherent ergonomic constraints of the desktop environment in mind. The above-linked 10/GUI concept is still the most compelling I've seen with these considerations in mind. Especially with successive generations growing up with ubiquitous technology, I really don't think dumbing down our interactions with computers is helpful.
[^1]: I'm not particularly interested in tablets because I always feel restricted even on laptops. To me, the tablet is an even more restricted laptop, one that's built much more for consumption than production. For a portable, I'm much more interested in the MacBook Air.
[^2]: Android's primary influence before the iPhone was the Blackberry. WebOS and Windows Phone 7 are widely regarded as excellent UIs (at least conceptually), while Blackberry OS's half-hearted attempt to convert to a touch paradigm is widely panned.
[^3]: Good app design can mitigate this, but not eliminate it.