On the whole, it’s actually rather un-Apple-like that they’re even allowing iPhone apps to run unmodified on the iPad. It’s a huge compatibility win, of course: an instant market of thousands and thousands of titles. Given the runaway success of the App Store and the fundamental technical similarities between the iPhone and iPad, it’s the sort of decision that most companies wouldn’t even think twice about. But it’s undeniably a sub-optimal user experience. iPhone apps on the iPad are a “good enough” thing, not an “exactly right” thing. Most companies — the ones that wouldn’t even see it as a tough decision whether to allow iPhone apps to run on the iPad — settle for “good enough” all the time. Apple, on the other hand, usually goes for “exactly right”.
— Daring Fireball: iPhone Apps on the iPad
