The iPad, like the iPhone and iPod Touch, will sync via iTunes to a host computer that provides its software updates and backs up its data in case of mishap. The iPad is thus potentially a companion device rather than a main machine. This may not be a problem to existing Apple customers, who have a computer and happily sync their Apple-designed companion devices to that computer using iTunes, but one of the apparent advantages of the sub-$500 price tag is that it would seem to appeal to folks with a sub-$500 computer budget. If Apple tells these folks that they need to buy some other machine in addition, Apple may be talking itself out of a sale.
How the iPad's specs play into this companion device meme? Straight off, I note that it has a maximum capacity of 64GB. You can get an iPod with more storage. Lesson? You need someplace to put your data, because it doesn't fit on the iPad.
(Note: I say this as the owner of a machine with 2TB internal storage, a large music collection, tens of thousands of photographs, and lots of fax-email transmissions filed away in various folders along with other records of projects to which they relate, which projects may contain multi-megabyte documents and presentations. The putative netbook-vs-iPad customer I hypothesize is very unlikely to have this quantum of data, or it would be on an existing computer with vastly greater power than exists in netbooks. I may be making a big deal out of nothing. However, I point this out to invite questions and discussion of Apple's strategy.)
On the bright side, the 64GB of storage is fast, low-power, solid-state flash that supports Apple's program to deliver battery life. A quality-of-life issue working in iPad's favor is that a user will never, even in some kind of energy-conservation mode, have to wait for the hard drive to spin up to access a cache file, save a document, or do anything else involving the filesystem: the solid-state drive is always ready to go, and it's quiet so nobody is bugged when you save files or the operating system synchronizes its cache or swaps.
(And the iPad will save files, as it supports content-creating applications. Apparently, managing files will be the responsibility of the files' applications and the user will not be asked to know anything about the filesystem. Let's hope developers come up with high-quality mechanisms for sorting and finding the files users will handle.)
Since the iPad will, according to Steve Jobs, allow users to make documents and to save them in various competing but common formats and to email them without having to access some kind of host machine, the iPad is much better suited as a stand-alone device than initially supposed by Walt Mossberg when he approached Apple's CEO on the subject of sending in his review from the device (to editors who could not read iWork's native formats). Unlike the week-long Kindle charge, Steve Jobs (in the same interview) made clear that he didn't think that plugging the iPad in daily was a burden for anybody. As a person who's been bitten by failure to plug in an iPhone in a confusing or busy night, I can attest that a one-day charge can limit people – especially on a multi-day road trip. On the other hand, in a multi-day road trip one would expect access to a car's DC outlet and a recharge; classrooms have power outlets; school lounges have power outlets; airports have power outlets; some airlines support iPod recharging; and there are recharging solutions for iPod-compatible sockets that appeal to virtually any circumstance a user might imagine (aircraft-headphone-jack-to-iPod-connector recharging?). These don't prove the recharging problem doesn't exist, though: they prove that vendors will sell users a crutch to overcome battery limitations in iPod-connector-equipped Apple products. Still, with ten hours of video, one can do much more than one would have expected with a notebook's battery life.
"The history of tablets has been that they've all been failures, and the question is ... can you create a market for something that never had a market before by making it better as a device or by delivering a lot of content or services that other tablets didn't have?"
This is really the question for Apple. Will Apple grow the tablet market like it did the market for MP3 players, or will the iPad join the other skeletons drying in the desert of tablet devices?
I think Apple's bid to grow the market depends in part on its success in pitching the iPad as a stand-alone device and not as a mere companion to real computers.
(UPDATE: Mule Design's Mike Monteiro predicts the iPad will be sold to users instead of notebooks, suggesting a belief the iPad will – whether immediately or down the road – offer an experience free from the orbit of a "real computer" because it will itself be sufficient computer. The Mac Observer's Dave Hamilton says he's sure that the notebook replacement is where Apple is heading with the iPad.)
UPDATE: Mossberg agrees:
If people see the iPad mainly as an extra device to carry around, it will likely have limited appeal. If, however, they see it as a way to replace heavier, bulkier computers much of the time—for Web surfing, email, social-networking, video- and photo-viewing, gaming, music and even some light content creation—it could be a game changer the way Apple’s iPhone has been.
"Laptop Killer? Pretty Close" by Walt Mossberg