Like just about all semiconductors, LEDs are advancing according to Moore's law - performance is nearly doubling every 18 months or so. The typical measurement for efficacy (efficiency) for LEDs is lumens produced per watt. The "gold standard" from the early DIY days was the Cree XR-E, which topped out just under 100 lumens per watt for cool white. That was a year or two ago. This past winter, the Cree XP-G came out, which is around 140 lumens/watt at best. Cree has announced that this fall they will have a new LED out. It will probably approach 200 lumens/watt.
So, really, it's like any other electronics. You can go buy an iPod today, and next year there will be a cheaper one that has twice as much storage. So you really just need to decide if you want LEDs now bad enough to jump in, or if you're OK holding out for a year and seeing what happens.
FWIW I really don't think any of the current commercial LED products for the reefkeeping hobby are worthwhile, unless you've got bucks to spend. Few of them use best-of-breed LEDs, and those that do are typically around $25 - $30 per LED. On the other hand, it's common to DIY a fixture with the same or better components for $15 per LED.