According to Apple's latest press release:
“Customers around the world are experiencing the magic of iPad, and seem to be loving it as much as we do,” said Steve Jobs, Apple’s CEO. “We appreciate their patience, and are working hard to build enough iPads for everyone.
Developers have created over 5,000 exciting new apps for iPad that take advantage of its Multi-Touch user interface, large screen and high-quality graphics. iPad will run almost all of the more than 200,000 apps on the App Store, including apps already purchased for your iPhone® or iPod touch®. "
here's a fun video showing few reasons why...