Even coverage is a main difficulty with LEDs. Many have found that they have to use quite a few more units over their tanks than suggested by the manufacturers, especially for finicky SPS. An excellent approach to LED configuration is illustrated by the LANI system where the LEDs are run at lower power, but there are many more of them nearly covering the entire tank. Both of these methods are quite expensive, however.
Hard to dismiss that a T5 + LED hybrid is a more cost effective solution. There is even a LED tube now that mimics a T5 in shape consisting of many LEDs in sequence, so that's another possibility for those who want to go 'all LED' and not have to replace bulbs, but still keep the T5 spread/form factor:
http://www.reefedition.com/euroquati...aquarium-lamp/