[I] think they're a bad idea and shouldn't ship enabled by default. […] The touch screen is now an input into two systems: the application and the operating system. Despite the utility I believe this is a step backwards and certainly a trade off I'd be hesitant to make so early in what will undoubtedly be a long-lived product's life cycle.
Maybe Apple agrees with this multiple-abstractions argument (it's a good one) and this is why the gestures can't yet be enabled easily by the general public, but honestly, at this point I just can't imagine using my iPad without them. For me, the gestures make the overall iPad experience a lot more fun, and a lot less annoying. They're a big deal to me, and I'd be more than a little pissed if they were taken away before a comparable solution was introduced.
Gruber generally agrees with Guy, and then says:
And please, stop with the predictions that these gestures suggest future home-button-less iPads or iPhones. Try explaining to a normal person that they need to use five fingers to get back to the home screen. People love the home button.
I'm pretty sure if my dad read what John wrote above he'd have no problem understanding that five fingers are needed to get back to the home screen. Indeed, I don't see how that's any more difficult to explain/learn than that the button takes you back to the home screen. Frankly, apart from people that have less than five fingers on one hand, I can't understand why anyone wouldn't prefer this method.
Also, I'm not sure people love the home button; they simply haven't been exposed to any other option. As it stands, I use the home button only to wake the iPad when I'm not using the Smart cover (which, obviously, I could do just as easily with the power button on the back), and would be apathetic if it was removed tomorrow.
Guy offers a few alternatives for inputting multitasking signals, and at the very end of his piece mentions "bezel gestures." These I think ultimately will become the standard, because they likely won't break the functionality of any app, and can be made to shift around the bezel relative to the device's orientation, so that, as with on-screen gestures, the controls are consistent no matter how you're holding the device.
(If you'd like to enable the gestures, see this.)