Light Emitting Diodes (LEDs) aren't yet a generally able to replace incandescent bulbs. They're not bright enough or cheap enough, and it's hard to make a focussable LED light, so practically none of them offer a narrow spotlight beam. But they've also got considerable advantages - functionally infinite lamp life, excellent shock resistance, availability in a range of colours without the need for power-wasting filters, and useful light output even from almost-dead batteries.