Also, I think more technical use cases where a larger touch device can be a control surface could be important as well. A few obvious applications are MIDI controllers, video application controllers and others applications where complex mechanical controllers are used.
No, they don't. Microsoft got raked over the coals in both the courts and public opinion for making it somewhat more inconvenient to use third party browsers and media players. Under Apple's policies third party browsers and media players are entirely prohibited, and that's just a side effect of their complete control. If Microsoft had that kind of power 20 years ago, the web wouldn't exist. Likewise if the iPad and similar devices take over, Apple will be in excellent position to block the next major innovations that might interfere with their established business models.
Regulation is hard.