> They were fluorescent and took awhile to brighten up, so of course this meant that one would enter a darkened room, turn them on, and then slowly get some light. Was it a huge deal? No. Did it make our lives worse than just leaving the lights on? Yes.

LEDs don't do this. At absolute worst, you'll have a fraction of a second before they light up at all, but once they light up, they light up immediately.