Wow, it's good to get back on the forums after a long break and see how we've progressed to LED lighting in the CP world. Now, to the meat and potatoes. I agree that LEDs have great potential. The problem is that there has been little REAL development in them for use with plants. Yes, the ones ya'll have mentioned are more or less in the right direction, there is still much left to be desired. This is the exact thing I am researching for my Master's thesis so we are doing a lot of experimental work with LEDs. The problems with the high output lights is that passive cooling has not been adequate for cooling unless using a pretty significant heat sink. It would also be worth noting that LEDs lose a lot of efficiency if they get hot so the heatsink is particularly important. Even the ones in our greenhouses have lost some of their "gusto" from the summer heat.
Ya'll have touched on this, but I'm gonna jump a little further on this; the nice thing about LEDs (and sometimes a problem too) is that they are manufactured at a very specific wavelength. So you gotta get pretty specific when choosing colors.
I have found that dimmers are an absolute must. Since LEDs do fade and lose power over time it's important to be able to get adequate light early on at a lower setting and then bump things up as necessary. We try to give our plants ~100PAR and as noted ours lost some power over the summer from the heat and I had to go in and adjust the dimmers to get my PAR back up.
I'd be very interested to see pics of anyone's setup and get some technical specs if anyone wants to share. I love this kinda stuff... which is why it's my field of research... LOL
Finally, there are some LEDs that have been specifically tailored to plants. Phillips has their GreenPower lights that I am specifically working with
http://www.ecat.lighting.philips.com/l/oem/led-systems/led-horticulture/20556/cat/#. There is also Orbitech
http://orbitec.com/store/led_lighting.html. These are the ones we are currently working with. There are other companies out there, but it's important to note that a lot them are making some pretty wild claims based on little no research. I would know, because I'm one of the ones doing that research.