Thanks for starting a thread that actually is attempting to have a POSITIVE view on what is one of the most contravertial technologies in the grow community!
I have only been on this forum for about 6 months or so and had mixed input about LED vs "other" light sources. I began the idea of growing 2-4 plants at a time at about 18-24". I wanted it to be in a cabinet for a few reasons. I found the cabinet first, then worked back from there, but had already lookied into lighting sources first.
The internal specs of the cabinet are 38"h X 40"w X 22"d. I found it at a thrift store for $17.50 and knew it would be ideal.
I knew now that temp control was the first concern to address. Even 150w HPS was going to be too big of a pain with ventilation and giving enough distance between the tops of the plant and the light. I found a "UFO like" 90w 660nm and blue light on ebay for $140 including shipping, so I settled on that one.
I lined the entire interior of the cabinet with mylar and flush mounted the light to the ceiling after cutting circular holes where the fan ports on the light were.
My first attempt at flowering was with 2 plants. One was a strangely pruned mother plant that had very few nodes on it. The other was a samll seedling that was 11" with few off-shoots. This resulted with 6 8ths. At this point I was happy with good bud. I then did another full grow that contained 3 strains. 2 were like the mother in the first grow, 1 was like the 11". The 3rd one was a new strain that I hadn't flowered yet.
During this grow I realized that I was nute burning all of my plants, but the new strain took it poorly and locked up pretty bad. I didn't notice until week 6 of flowering that I was feeding TRIPLE the nutes my mistake!! ( was feeding Tbs. instead of Tsp.)
Once this issue was corrected, all 3 strains exploded with growth!
I began flushing with just water in a hydro setup at week 8 and harvestedat 10 weeks. I would have let them go longer, but I had plants ready to go into Flower that I had been keeping short and bushy. After drying for a couple days, I ended up with 54g and that was with the burned plant yeilding only 3.5 g. That was 0.6g/watt which is respectable to most that I see on this forum.
The one thing I will say from my experience is that LED is a great light for what I wanted to do. There is no heat control that I have to do and the cabinet peaks out at 81 degrees. Humidity is more of an issue than heat.
I can't speak for how well LED would do in a large room with huge plants, but it is great for a cabinet.
I have 5 plants in my cabinet now and they are avg. of 16" tall when they went in. These plants have over double the nodes from the way I trimmed them during Veg. than the ones in previous grows I have done.
I also installed 2 CFL floodlights (23 watts each) on either side of UFO light to attempt a fuller spectrum of light.
LED I think is best for people that are wanting to grow their own bud without drawing attention to themselves.
Grow well! (Sorry this got a little long, lol)