Like nearly everyone else said. I use one for my HT room and, once properly programmed (you go to their website and input all the info about your audio and video equipment, then connect your Harmony via USB and program the sucker), you can hit one button to 'play music', 'watch TV', or 'Watch a DVD' and it will turn on all the equipment and switch the audio/video inputs so there's nothing to do but enjoy. My amps are the only thing I need to switch on and off manually. My wife was ready to kill me before I got the Harmony, and I found one for a great price on e-bay.

I would highly recommend you buy rechargeable batteries for it too, because they get eaten pretty quickly. Mine takes 4 AAAs, and I keep a charged set on back up so I don't have any down-time.