Isn't it a completely optional feature? Otherwise, Windows 8 would not work on any pre-Secure Boot PCs.

The article states that "According to Microsoft’s presentation at //BUILD/2011, Secure Boot will be “Required for Windows 8 client”"

For machines that adhere to the Windows 8 logo program. Windows 8 itself will still boot on BIOS, let alone UEFI systems without secure boot.

Pardon my ignorance, was Jobs obsessed with symmetry?

The white plastic Macbook has screws that appear to be purely decorative, on the left side of the case . The story goes that Jobs insisted on them being there, to achieve symmetry with the functional screws on the right hand side.

Yes. Many Apple products are very symmetrical, even looking at our old iBook G4, there has been an attempt to make it as symmetrical as possible.

This [1] was after Jobs stepped down as CEO, but it was obviously being planned while he was chief. The company went to an almost excessive extent in order for the store to be symmetrical.

[1] http://www.macrumors.com/2011/08/30/new-apple-retail-store-d...

He did seem the obsessive type, however given that there is hardware asymmetry (the camera, volume mute etc) I doubt he was.