I have grown several grows under LED and they all have been successful. I use DWC and have a very small growspace (600mmx600mm). I tried growing two plants but as one of the other respondents pointed out - no two plants are exactly the same and I found one always over-grows the other. I therefore decided to try to grow one plant exceedingly well and fast rather than two poorly and slow. This has turned out to be a winning strategy (my average crop-weight per month improved).
On the subject of light you need to understand (particularly with LED's) that there was a breakthrough in LED chip technology about 2 years ago. The light output rocketed. If you are going to use LED's you need to know who's LED chips the manufacturer is using. If it is Bridglux or Cree you may be ok. If you are using an old, crappy Chinese unbranded UFO you will be wasting your time, money and effort.
I am currently using a new Vipar that
really pumps the light out.
http://www.viparled.co.uk/ You also need to know that you should not go above 50,000 lux. The plants cannot use more than this - they are saturated. If you go really high (say 90,000 lux) you get solarization that will stop photosynthesis. I adjust the light intensity by lifting the light on its yo yo until it is at 50,000 lux at the scrog canopy and hold it there. My technique is to grow very fast (I choose fast finishing strains) and go for a high quality grow. I can also anticipate the next cycle by about 2 weeks by getting the next grow underway in peat plugs and then in a net-pot in clay balls waiting for the plant in the grow-space tank to be finished. Be cautious with this as some plants mature a little slower than others and you need to know the strain you are growing to pull this stunt. Different strains - different finishing speeds. I see no reason the same practice could not work with a non-DWC grow.
This technique is producing more finished high-quality bud than my wife and I want to consume. My stash got to heroic proportions and got risky from a legal standpoint (if your stash is too big and you get busted they can allege you have intent to supply - even if like me, this is nonesense). I therefore had a 5 month holiday from growing. Lastly - remember you will need a lux meter to measure and control light dose. These are cheap enough so don't try to grow without one.