LED is absolutely a proven technology, impossible to argue against it even with experience to the contrary. Sounds stupid to say this, but the simple irrefutable fact is there are thousands of reef tanks running full LED lighting in an almost unimaginable number of color configurations and most all of them are still on the tank and getting great growth. YES people as individuals have had issues, but the VAST majority LOVE them. The majority of issues are in the DIY setting which is impossible to trouble shoot case to case as they are all different.
Yes, early commercial fixtures might have been well... early essentially DIY fixtures from a company and results were spotty. Its come a LONG way in the last 3 years. Try it. You will almost certainly like it.
People who have tried and had issues likely complain about spotting, hot and cold spots (i.e. difficult to place corals) or poor color.
Typical problems are with design-
Lens angle is CRUCIAL- if you mount a fixture 6 inches off the water with 30 degree lenses your going to NUKE the bottom and have almost no light but for extremely intense light cones coming down from the top and getting wider as you go. This will lead to serious issues with coral bleaching depending on if its in a cone or not- as well as serious color blend issues.
Color mixing, same issue, pick a fixture height and lens angle that will fill the top of the tank with light that then naturally fills down through the water column and is attenuated as you would expect. Then-mount the LEDs as close as your willing (with adequate cooling) and colors will blend.
Color rendition-
Still kinda out there, everyone has a different look they like. This is NOT a growth issue. Its a my favorite color is blue and yours is purple blue and someone else loves red issue. Best bet is to LOOK at tanks with different fixtures- as many as possible. Then either buy the look you like, or build one based upon what you found and liked. I have heard from people who live where they can snorkel and also keep tanks, and the consensus opinion is that nothing looks as brightly colored in the ocean! Our tanks do an AMAZING job at turning nature into a technicolor dream world that is very far from nature as you observe it in the ocean. ANY light source commonly used will work.
I use Royal blues, Neutral white, "UV" and very very few blue/cyan. As an FYI... the "UV" leds have NO UV in them, they are simply super low wave length VISIBLE light, like a faint purple. YES it hurts your eyes to look into them (not recommended) but they really are not producing true Ultra VIolet wavelengths which would be dangerous and painful.
Some people argue you need more red.... well... the corals likely don't care in terms of growth since the ocean is probably deeper than 12-24 inches where they grow and water sucks up the red wavelengths pretty fast- but it does, some people claim make a difference in VISUAL perception of color. I have not tried reds. I have talked to a few people that have, so far (and its really only two people) they are pretty sure they would not order it with reds again... others like it.
You will get great growth- I can guarantee this if your using an appropriately designed fixture- DIY means read, research, etc. COmmercial is more like, find someone with X brand and go look. If you want to see a DIY LED tank, your welcome to come check out my tank. Just PM.
By the way, if I could EASILY add reds I would probably try it to see if I liked it... but I am in NO way interested in spending money for this, because I am perfectly happy with my color now. Maybe tomorrow I will see a tank with reds that is really really MUCH better (in MY perception of color) and go buy some... but so far its all about what you like to look at- not growth. Were past that argument, LEDS grow coral JUST fine, so do T5, Halide, PC (if you have enough).
I look at it this way, there are A LOT of different types of Halide bulbs in terms of color temp. THEY all grow coral- they do look different. Same with LED but probably 500 different possible combos if you DIY it. I WISH in some ways it was easier to say get XX but that fact is all those halide bulbs are still around and different people SWEAR by their favorite- so this is not ever going to change regardless of LED/T5/Halide/The next great thing.