Allow me, if you would be so kind.
A garden tractor and a motorcyle each serve a purpose. One is primarily designed for productivity, the other for leisure.
Consider the laptop. They weigh 4-15lbs, have a battery life that is 2-6hrs, cost $500-2500, have a keyboard, mouse and a screen. This is a productivity device. The monitor is designed to fold over the keyboard, typically you expect to use this device for limited periods with a battery, but primarily with the adapter plugged in. While you could watch a DVD on it, listen to music or read a book with it - most people do not. Why? Because the experience is sub-par. Most travellers with a laptop also travel with an iPod. If you fly a bit, the laptop is in constant danger of being destroyed if the seat in front of you suddenly reclines. The laptop is bulky and awkward.
Now the iPad. Let's start with the fact that there is no keyboard or mouse. You can hold it in ANY orientation. You touch your finger to launch any application, read or view any media. The display is IPS, far superior to ANY competing laptop. Cost is $500-700 for the non-3G version. The weight is 1.5lbs and the battery life is 10-12 hrs of actual use. Re-charge time is about 2-3 hours. Movies look fantastic on this display, as do Kindle or iBooks. This is a leisure device. Sure, I have Numbers (Excel), Pages (MS Word) and Powerpoint (Keynote) on mine - and I could use them if my life depended on it. But, that's a productivity suite that I use at the hotel room when I unpack my laptop.
With my iPad, I have a small, light powerhouse. I surf the net, send email, make reservations, play games, watch movies, listen to music, read books, newspapers, magazines ect on my iPad. My laptop travels in my carry on. With a lot of time to spend on a plane, I can be 'entertained' for 10-11 hrs.
Hope that helps.