The only difference that I can think of is that the iPad is capable of going online with 3G service, but you have to pay extra for that. Think of it as a more portable laptop that can go online anywhere (with 3G) but no USB ports or memory card slot.
To answer your question: Personally I think it is useless. It is more portable than a laptop but it has way less capabilities of a laptop and its processors are noticeably slower than a normal laptop. The only good benefit I see is that it is much thinner, smaller, and lighter than a laptop, but I'll take a laptop over this any day.