Recently, in possession of an iPad2. Is it just a bigger iPhone, which is not capabele of making phonecalls ? Well, because they both use the same iOS operating system, and because many applications suitable for both devices you would almost say yes.
But most apps have an ajusted user interface, using the bigger screen for the iPad. Therefore, they work slightly better than on the small screen of the iPhone.
The application I am using the most on my iPad is Evernote. Very handy to take notes during meetings and sharing those with my other devices through the Cloud.
Another application is iBooks, great for reading books on my iPad and sharing bookmaks with my iPhone using the Cloud, to continue reading.