Stock image of the honeycomb graphene structure
Graphene is almost assuredly poised to replace silicon based devices in the future. From low cost, faster electron movement, to cooling effects, and now showing of a transistor that can operate at 155Ghz. IBM showed off its record breaking graphene transistor as of April 7th, 2011, defeating their previous record of 100Ghz set in February of 2010. IBM conducted the research to make a high-performance RF transistor for a DARPA project. The gate length of this new transistor in 40 nanometers, down from 550 from the 2010 demonstration.
The main issue with why graphene has taken over for silicon is the energy gap of the material. Graphene, at the moment, does not have a deep enough ratio to create and on-off digital switch. However, the constant flow of energy makes graphene excellent at processing analog signals. According to IBM researcher, Yu-Ming Lin, "Graphene's high electron speed allows for faster processing of applications in analog electronics where such a high on-off ratio is not needed."
Our 155Ghz computers still await more research in gaphene, but IBM is definitely showing off a little glimpse at the future.