Danish doctor Jakob Nielsen, called "the guru of Web page usability" by The New York Times, has a bone to pick with the iPad's user interface. A lot of bones, in fact — 93 pages of them. That's a hell of a lot to read, but luckily the good doctor has provided a summary of how he feels:
iPad apps are inconsistent and have low feature discoverability, with frequent user errors due to accidental gestures. An overly strong print metaphor and weird interaction styles cause further usability problems.
Nielsen goes on to say that the iPad doesn't benefit from its iPhone UI, and that the features it shares with its smaller cousin don't work as well on the big screen. Much of it boils down to this: "a usability problem we haven't seen since the mid-1990s: Users don't know where they can click," and the assertion that there isn't a sense of depth to the iPad's presentation. In other words, it's flat.
So, how could Apple improve its iPad UI? "Add dimensionality and better define individual interactive areas," Nielsen writes, adding that there should be "support [for] standard navigation, including a Back feature, search, clickable headlines, and a homepage for most apps."