Samsung's HL-S5679W HDTV ($4,199), coming in August, is the first rear-projection set to use LED (light-emitting diode) light sources instead of a conventional lamp. Among the reasons you should care: a 20,000-hour lamp life (more than double typical lamps), a shorter turn-on time (7 seconds), and being able to rattle off one more abbreviation when blabbing about your rig.