I have to nitpick because that's a very frequent misconception as well: electrons, in fact, move very slowly in metals and semiconductors (a few cm/s at best). It's the electromagnetic waves that move so fast (depending on the material, it's going to be anywhere between 0.5c and 0.9c in most everyday appliances), but the electrons themselves are really slow.

I always went with this:

Principle of physics is that Light and Electricity are the SAME THING. Electricity is just Light guided along wires. [http://scienceline.ucsb.edu/getkey.php?key=2910]

Than the following link shows that electricity moves about 1/100 the speed of light in wires:

Light travels through empty space at 186,000 miles per second. The electricity which flows through the wires in your homes and appliances travels much slower: only about 1/100 th the speed of light. Part of the reason is that light is massless; it has no weight, whereas the electricity flowing in the wires is made up of a stream of electrons, all of which have some small amount of weight. In addition, the electrons flowing through the wires constantly bump into the atoms of the wire, which slows them down considerably. If you were to take the electrons out of the wire and make them flow through space (which is essentially what you do when you make a spark), they can move faster, but no matter what, they cannot move as fast light. [Light travels through empty space at 186,000 miles per second. The electricity which flows through the wires in your homes and appliances travels much slower: only about 1/100 th the speed of light. Part of the reason is that light is massless; it has no weight, whereas the electricity flowing in the wires is made up of a stream of electrons, all of which have some small amount of weight. In addition, the electrons flowing through the wires constantly bump into the atoms of the wire, which slows them down considerably. If you were to take the electrons out of the wire and make them flow through space (which is essentially what you do when you make a spark), they can move faster, but no matter what, they cannot move as fast light. [Light travels through empty space at 186,000 miles per second. The electricity which flows through the wires in your homes and appliances travels much slower: only about 1/100 th the speed of light. Part of the reason is that light is massless; it has no weight, whereas the electricity flowing in the wires is made up of a stream of electrons, all of which have some small amount of weight. In addition, the electrons flowing through the wires constantly bump into the atoms of the wire, which slows them down considerably. If you were to take the electrons out of the wire and make them flow through space (which is essentially what you do when you make a spark), they can move faster, but no matter what, they cannot move as fast light.[http://scienceline.ucsb.edu/getkey.php?key=2910]]

Thanks, edited to clarify.

You're welcome :).

You're right that there's a pretty limited benefit to simple signal transmission, but when it comes to switching and capacitance, there could very well be more significant gains.