The iPad is great for many things, but it's fundamentally a consumption device and isn't great for serious office work. For example, when I'm doing research I often have 6 or more "spaces" open with dozens of documents and websites and I need to be able to switch documents and applications easily, and most importantly, to have multiple documents on screen at the same time.
It also lacks many specialized applications that are only available on Windows or OS X, and is very difficult to get any kind of programming or web development done on.
Finally, it isn't powerful enough to do any kind of professional video editing or play modern video games (yes, iOS has some fun games, but it's nothing like the immersive experience of PC gaming).
I'm not trying to bash the iPad here (I love them), but they are only good for what they were made for: consumption. They are great for browsing the web, doing e-mail, listening to music, reading, and watching movies. They are even good for taking notes and some other light writing, but not if you ever have to have multiple documents open at the same time.
Great !!
Thanks