I use a lot of the photosynthetic analysis work by Dr. Bruce Bugbee in my consideration of lighting strategies.
I use LED and HID lighting mostly, but have a couple of compact fluorescent lights as well that I sometimes use.
I've become very fond of High Bay LED light fixtures (in the 150-200 watt range) designed for lighting workshops. I also love 315 watt Ceramic Metal Halide lighting, which is the closest thing to the sun aside from sulfur bulbs so far.
For cacti my lux ratings are between 18,000 and 26,000, depending on the lighting and I use from 40-70 watts per square foot, with all types of lighting. I also gauge distance from a light by heat using my hand as well as a thermometer to make sure that temps are not too high.
However I expect that specialized laser lighting, like the type used on recent models of Rolls Royce automobiles, will revolutionize indoor plant lighting just as soon as people start applying the technology to indoor growing. Unlike the lighting we use at present, this type of lighting has a very similar photo intensity 1 foot away from the lamp as it does 10 feet away from the lamp and has extremely practical applications for growing crops indoors.
