One of the reasons I'm excited about a built-in second screen is, I don't need to carry another extra device. I mean even if I need to use an ipad, I'm currently slouching on my couch. I need a flat surface to keep that ipad/screen at the right angle. Sounds petty but it's just very convenient to have more real estate on your lap (or on a flight or cafe table).

Also, I'm not too into the Apple ecosystem and don't own an ipad so would have to get an ipad just to use it as a second screen. I think it could work for some but an integrate dual screen solution is exciting.