Nilay Patel, The Verge:
As for using the thing, it really feels like what Dieter Bohn is calling an “iPad mini mini” — turn it into landscape and there are riffs on the iPad two-pane interface everywhere. There’s also a new wider keyboard with extra keys including dedicated cut / copy / paste buttons and arrow keys, and new notes and emails open in a â€œsheetâ€ over the main interface. Itâ€™s unique, in the sense that Apple is very good at crafting distinct interfaces for distinct screen sizes; Android just gets bigger at larger sizes but iOS gets different.
The 5.5-inch iPhone 6 Plus will cannibalize some sales of the iPad mini. Even though the difference in display size is not trivial the convenience and simplicity of not having to take around and manage two separate devices could be enough of an incentive.