I have seen several tanks set up with LED lighting. First off, the LEDs are set up in banks or clusters with a big dead space until the next bank. This makes for a very unnatural looking tank. There are big dark spots between the bright (or should I say Lit) spots. They are not bright enough to keep most corals alive. Of the three tanks I saw with LED setups, all three tanks appeared to be dying setups.
All in all, I would not run these lights if they were given to me for free! They may hold some promise in the future, but the future is not here yet.