The iPad is an entirely new class of device. Should not be thought of as a netbook or small computer, nor a large iPhone. Rather it brings an entirely new level of touch based, visual mobile experience. It will become one of the preferred ways of experiencing the Internet and social networking, distinctly different from computers, netbooks and phones.
The critical element to understand is what happens when a rich visual and communicative experience enable by a touch-stroke model is opened up by a larger screen, essentially always connected. iPhones etc are great but fundamentally too small for a certain level of experience. Computers and netbooks are derivatives of keyboard and mouse experience and even with a touch scree are a modal, more rigid structural experience. Similarly, even though PCs in many ways are more powerful than video game consoles, they are not optimized physically nor the software architecture matched to the optimal physical handling of video game consoles. The game play effect of game consoles cannot be fully replicated on PCs.
Back when I was at Apple when we went from the Mac Plus to the Mac II we all thought the sea change would be the flexibility of the expansion slots. But it turned out to be the large screen monitors. The larger screen real estate opened up the value of the Mac's graphical experience. Similarly the larger but still mobile convenient screen of the iPad will open of the value of the touch experience on the web.
More intimate, mor social: This is partly just being able to see things larger and more of them. But more so the ability to glide ones fingers across the experience connecting mind and heart to the stimulus of rich graphics/photos/videos, even more so to web content and even more so social interaction will expand the individual and group experience. The iPad is also more social in person. The larger screen, the tocuh stroke interface allows and motivates one to share the experience with others. A PC or Netbook is physically too awkward for this. The iPhone's smaller screen doesn't come close.
Brand marketing impact: The deeper emotional connection, visual and touch stimulus combined with its mobile conveniences opens the possibility for a brand to incorporate itself or its themes more into the consumer's daily life.