With all my mumbo-jumbo about conjuring up spirits and casting spells, it's easy to lose track of the fact that computers are real and there is a very precise and concrete connection between the programs and fragments of code you run on your computer and the various electrical devices that make up the hardware of your machine. Interacting with the computer makes the notions of computing and computation very real, but you're still likely to feel shielded from the hardware – as indeed you are – and to be left with the impression that the connection to the hardware is all very difficult to comprehend.
For some of you, grabbing a soldering iron and a handful of logic chips and discrete components is the best path to enlightenment. I used to love tinkering with switching devices scavenged from the local telephone company, probing circuit boards to figure out what they could do and then making them do something other than what they were designed for. Nowadays, it's easier than ever to “interface” sensors and motors to computers, but it still helps to know a little about electronics even if you're mainly interested in the software side of things.
I think it's a good experience for every computer scientist to learn a little about analog circuits (for example, build a simple solid-state switch using a transistor and a couple of resistors) and integrated circuits for memory, logic and timing (build a circuit to add two binary numbers out of primitive logic gates).