The ability to run android apps - like bb10 on blackberry? That's upset a few people!
I'm pretty sure it is the 3D gestures. It would, after touch screen smartphones be the next revolution among smart phones. IPhone was the touch revolution, the McLaren will be the 3D gesture revolution if well implanted.
What I hope most, no matter what it is he refers to, is that neither Google or Apple can copy it within 2 years. That would give WP enough time to take over smartphone world.
All in all has to be a feature or overwhelming thing that makes people want to forget the app gap and choose WP anyway. Just as when people took an iPhone simply for the new experience, leaving behind much more functionality that was at Windows Mobile.