iPad is not ready for success yet.

See this youtube bellow, during Steve demonstrated his iPad,
No matter how he try to sit, he still can't put the iPad down and use it in a easy way.
He always have to use one hand to hold the iPad and operate it using the other hand.
He will get tired pretty soon, same as users in the future. It can't really put on people's laps top to operate in two hands as a lap-top (notebook) does. That's why tablets never work well and sell a lot.

The major problem is the screen and the virtual keyboard or touch screen are on the same surface, you can't adjust the angle to your eyes as easy as a notebook or netbook. The size is still to big to hold for a long time as mobile phone. That's why people won't like it very soon after they buy one.

I hope it's just my personal idea. Hope Apple can find a good way to hold and use this kinds of devices soon in the near future.