There's No Button Like the 'Home' Button
If you believe the folks at Boy Genius Report, Apple is testing models of the iPad and iPhone that substitute multitouch gestures for "Home" button; although such a design might appeal to Apple's maximal leader and CEO, I suspect it will prove to be a huge mistake if implemented.
That's because one-handed use is essential for most of us, especially on the iPhone. After several months of using the last couple of iPhone models, I've become rather comfortable with controlling commonly used features with my thumb, and I honestly can't see how one could use multitouch, keep a grip on the phone, and still hang on to a stanchion in a crowded bus, streetcar or subway. Then there's the question of how one would use a multitouch iPhone while operating a vehicle; you're asking for a lot of small muscle coordination at the same time you're trying to keep your car in a freeway lane.
Those of us who were paying attention to Apple 25 years ago might recall the story about the choice of a single-button mouse for Mac being driven by the way it made documentation simper to write. Much more recently, there was a rumor that one of the reasons why the white iPhone 4 has never been released to the public is because the manufacturer of the Home button and the manufacturer of the front panel had produced their plasticware in slightly varying shades of white, allegedly spoiling the look of the whole device.
So it's certainly reasonable to assume that word has come down from the big boss that the home button has to go away. But such a decision would ignore the lessons taught by recent models of the iPod Shuffle. The first two Shuffle models had an easily operated set of concentric buttons; I can operate any of my Shuffles (I own two of the first-generation Shuffles and a second-generation unit) without once looking at the device, leaving it nestled securely in a pocket. The third-generation Shuffle had most of its controls moved to the headphones, and was rather poorly received in comparison to the first models--so much so that in the fourth-generation iPod Shuffle, released last year, the onboard buttons were added back to the design.
On top of that, I'm not a big fan of multitouch as implemented in Apple's trackpads. Part of this is because, after using clickable buttons on laptops for almost 20 years, I've developed a habit of resting my thumb on the button while I'm using the trackpad. This is a problem when using a multitouch trackpad, which interprets my resting thumb as being part of a gesture. I could train my thumb to hover as Jobs intended, but as someone who makes my living at the keyboard, doing so would be more trouble than it's worth; the last thing I need at my age is more muscle strain in my dominant hand.
I've disabled most of the three- and four-finger gestures on the newer Apple devices that I use, in part for this reason, and in part because I can't be bothered to learn yet another way to interface with my computers. Although some of the multitouch gestures have proven useful, for me the technology has proven to be as much of a nuisance on computers as it is a blessing on mobile devices.
With any luck, the people responsible for Apple's usability testing will come to similar conclusions. The worrisome part is that the higher-ups will reject those findings and foist a generation of half-usable devices upon customers.
UPDATED: Andrew Garcia had the brilliant idea of illustrating this with video; although it's hard to illustrate how a device without a Home button might work, it's a good depiction of how those of us with hands smaller than a flapjack might struggle with multitouch in a one-handed situation.