Ok that is the short answer. here's the longer answer.
The technology is too new, it is very expensive.
Short term it seems to be ok but there is no long term studies to prove if it is better than MH or t5 or just another substitute. In the long run as well there is little to show if light replacement is required. Oh and by the way how much is that gonna cost? T5's are proven so is MH. Heck even normal lighting and PC lighting are proven long term. I would stay away from it for a while. Also the price will come down when they get some competition too keep that in mind.