3 (Microsoft Courier)
There is no iPad here, nor Surface. Only abandoned Courier is a tool one can be equally productive as on two former examples. To be there, two applications side by side are not enough, a lot more is needed. I’m sure Apple will push into that direction, some APIs are needed, and it’ll start from the browser.
To push iPad Apple doesn’t need trials, only sophisticated clipboard:
The clipboard is a set of functions and messages that enable applications to transfer data. Because all applications have access to the clipboard, data can be easily transferred between applications or within an application.
Those people from Courier team really cracked tablet interface. MS decided again to push PC into tablets, as it did with phones, and again, it failed. Surface is just PC with stylus.(16 September, 2015)