Good points, fairchij.

I also had the presence of mind to ask Dr. Taylor about graphene at the 2011 AGM in TO and he said something like "the difference is compatibility"

Knowing what I know today I would have asked him if he was talking about compatibility in terms of manufacturing (which IBM claims is not a problem - it can work with existing semi fabrication techniques), or compatibility with other components in a system (E.g. graphene processors on a standard board interacting with Si memory, HDD, etc.)

As fairchij mentioned, the O in POET might just trump the ridiculously fast electron & hole mobility in graphene as light will transmit much faster.