Yeah, sometimes, when I am sitting before my computer and typing comments on the Internet, I have a thought: "Is my computer turned on?" With a quick glance under my table I can reassure myself that it is indeed on and continue using it. No idea what I'd do without that small blue LED.

The pilot lights are slightly more useful in those stupid cross-wired double switches that for some weird reason implement a sort of XOR (or sometimes XNOR because why not) gate for controlling a single light: if it's on, then the bulb is depowered and you can safely change it without turning off the entire power rail. But then one day the pilot light itself burns out...