Keep in mind a 100 GHz transistor will NOT make a CPU with a clock speed of 100 GHz. For a single clock cycle, each transistor may have to flip SEVERAL times; there needs to be enough done that each logic gate can at least process a cycle ONCE.
As the article noted, top-end silicon transistors currently top out at ~40 GHz, which would be about what Intel uses for their sub-4 GHz CPUs... So that means perhaps 10-12 transistor cycles per stock clock cycle.
Still, this is a very good piece of news; it's STILL 2.5 times faster than the currently-used tech, which means we could see CPUs with it in the 8+ GHz range. Furthermore, the fact is that they're building these out of graphene, a material basically similar to the so-called "nanotubes." (the difference being that graphene is a flat sheet, while nanotubes are fixed in a hollow tube-shape)
While the current mentioned "size" is listed as 240 nanometers, I'm not sure how that equates to actual process size equivalent, since logic gates tend to be longer than they are wide (they consist of a lot of transistors) and the "feature size" for fabrication processes typically goes on the distance when placed side-by-side. However, since this is basically nanotechnology, there's tons of room to shrink them down in size, potentially into the sub-nanometer range. (the distance between carbon atoms being about 140 picometers, aka 0.14 nm)