As I have played with Windows 8 (both the Developer Preview and the Consumer Preview), I have gotten the distinct feeling that it has been developed assuming a right-handed user. For example, access the system charms works much more consistently with my right thumb as opposed to reaching across with my left hand.
Tonight, while reading through some of the developer documentation for the consumer preview, I came across the following statement:
Apparently it is ok to ignore 10% of the population when designing your user experience.
FredSpace 