[magicalhippo]

Not just delays. Being able to drive a transistor fast can be important for reducing power dissipation. That is, for switching one wants the transistor to spend the least amount of time in the non-saturated (linear) region where it acts as a resistor.

[Ballas]

Judging by the process size quoted in the article, they won't be chasing speed, but rather low-cost devices.