[Skybird]

Let it be stable.
Let it be compatible.
Let it be tight and safe and secure.
Let it be supported by drivers.
Let it be simple in options, handling and structure.
Let it be running on as little ressources as possible.

Let it be the empty screen on which the film is projected. Let it not be mistaken for the film itself. Let it be blessed with the virtue of modesty, then.

For cars there is a simple rule: the less complex, the more solid, the fewer problems. OS-makers can learn some desirable goals from that.