Everyone thinks different of course but I think the five most crucial feature of ipad;
1- Wacom drawing tablet,
2- Instant messaging processor and video conferencing,
3- Universal remote; thanks to this feature in your home lighting system, home theater system, camera outside the door, even heating and cooling systems can control with your iPad,
4- Unlimited social game option with a multi-touch screen,
5- Will affect the e-book readers with virtually no training required use of and wide-screen features.