...I do *not* simply scale the existing iPhone user interface up to the larger screen. I actually try to make new use of those additional pixels and this has led to some features only being available when running on an iPad. I may be biased but I think this would count as iPad exclusive.
What he said. If you don't have an iPhone, when you load a "universal" app on your iPad, you may not realize how different it as compared to running it on an iPhone. Being new to iPads, but having had an iPhone for over a year, I've been very pleasantly surprised by this.
You might be able to get some sense of this by looking at a universal app in the iTunes store
on your computer (important); first looking in the iPhone section, then the iPad section.
Regards,
Tom