That isn't correct, search PlanetGanja and Cannabis boards and you can find a lot of threads on the advanced theories and practice of growing using LEDs, it mainly comes down to most people attempting LED grows are using inferior quality or simply not powerful enough LEDs. From what I've personally seen and heard a proper setup using high power aka class 2 LEDs (Cree Xlamps, Luxeon Rebels, and Ledengin (which come from individual wattages of 5-15W) would basically demolish all other currently availabe forms of lighting in PAR and PUR. The main arguements going back and fourth are beam angle related, underdriving vs overdriving, the use of light near 660nm to create artificial darkness.
With that inmind however, one must note at the current prices for these higher end components, initial cost is much steeper, however once one factors in electrical costs (assuming you aren't solar, wind, etc) it does indeed even out, even at this moment. I believe in the November 2008 issue of High Times Jorge Cervantes reviewed a Spanish built UFO type LED vs a 400W HPS and a 600WHPS, the yeild to electrical price ration in this particular example was a net loss of 15% of yeild however when costs were factored in this was nearly even, and I in no way assert this is the most effective design.
Please in no way insult the thousands of man hours being put into the serious and hobbiest application of LED technology as a long term revolution in horicultural lighting.
I my self bought a Chinese panel which is apparently underdriven unnamed brand 10mm LEDs in an array of 72 Red vs 40 Blue. I was a victim of misrepresentation, but from that mistake I have done significant amounts of research on the topic. I'll put it to you like my forum buddy Weezard put it to me, 5mm? Not It, 10mm? Not It Either, 1W, Little Bit, 5W Getting There, 15W? Can Do. He's using an array of 4x RED 15W 1x BLUE 15W underdriven so his guesstimation of total used wattage is 60, and the guy seems upright to me and he claims to have colas the size of his fist under that unperfected but raw power set up. here's a link to the thread where he responded to my questions for your own inspection
The perfect LED grow light - Page 60 - Cannabis.com Forums Message Boards - Medical Marijuana, Cannabis Club, Dispensary, News
Those Ledengin LEDs he is using are around thirty dollars per, but colas the size of my fist with a 60W power bill sounds like the future to me.
Not enough heat to keep them warm, and the main problem with led`s is that you can`t concentrate the light in one area. The bigger the spread of your array of lights the bigger the spread of the actual light coverage. That was crap, don`t do it.
I love them again. 
