I put some pictures of the evolution of some orchids under light led.
Bulbophyllum otoglossum

29/10/2011

20/01/2012

14/04/2012
Dracula mopsus

02/11/2011

14/04/2012
Laelia tenebrosa

20/01/2012

14/04/2012 --> With new pseudobulb.
Leptotes bicolor & Brassavola cucullata

04/11/2011

14/04/2012

14/04/2012
Masdevallia floribunda

02/11/2011

20/01/2012

14/04/2012

14/04/2012
Bulbophyllum otoglossum

04/11/2011

14/04/2012
All orchids grow very fast, my Catt. intermerdia, is growing very fast.
As a general rule, the leaves that grow a little smaller than natural light, I guess the LED light gives them everything they need and not spend so much energy with large leaves. That extra energy they use to grow many roots and many leaves.
The LED light is powerful, I have taken a while to find the perfect place away from light for each orchid, some need to be in the shadow of others to grow well. I guess with any artificial light to pass the same. Each orchid has its needs and must be respected.
I recently acquired carnivorous plants, and its growth is still spectacular LED light, these are in full light, which shows me that any plant benefits from the LED light.
My experience is positive.
Hugs!