OK, ok, we get it—the iPad's going to have us consuming media like it's our jobs. But to all of those it's-not-a-content-creation-device naysayers, the $8 SketchBook Pro app says, "check this out." [iTunes]
I am a graphic designer coming up on my 4th year of digital illustration. Anyone who can do art like shown above is not going to waste their time doing it on an iPad. My Intuos4 Medium blows this thing out of the water. Pressure sensitivity and the precision of drawing with a pen is leaps and bounds ahead of the iPad's sausage finger style.
And as for "drawing on the fly," that's why we have regular old paper and pen. An illustration, especially one such as the one pictured, is not something thrown together while you're out. 15 hours is the minimum I spend on a digital illustration final. That's not even considering the process, thumbs or roughs.
Think of finger painting vs graphite. That's why this will never replace a Wacom. Or spend the extra 500 bucks and get a Cintiq small. Those will blow your mind. This iPad app may be targeted towards professionals, but in the end, the hardware just isn't.
It's like putting a NASCAR engine in an Oldsmobile and expecting it to win the Daytona 500.