(Updated April 26, 2012, with two new keyboard cases.)
The one differentiating feature separating the iPad from portable computers such as Netbooks for many people, other than the operating system, is a keyboard. Yes, the iPad has its own onscreen virtual keyboard, but some will be tempted to explore alternatives to get "serious" writing done.
Keyboards for iPads have drawbacks: they add bulk to your bag, and the Bluetooth connection will add some drain to an iPad's battery life. You'll also have to consider whether you prefer a standalone keyboard, or a case that has a keyboard built in. Some cases have compressed keyboards, and others manage to fit a full-size one. You'll also have to learn to live without a trackpad.
For your comparison-shopping help, here are the keyboard cases I've reviewed. … Read more