I have red & aqua LEDs in a normal T1-3/4 case that are 10,000 candela or more. The Super Flux is only like half that.
Lumiled's Luxeon line is way, way more powerful than anything else. They come in 1, 3, and 5 watt emitters. The 3W emitter takes 700mA! If you've seen anything more powerful, then it's because they used several emitters. The 5W aren't a good idea, they lose efficiency so they don't put out as much light as they should, and cost around 3x more. The 3W ones are awesome.
The light is incredibly powerful, it's a bit more efficient than other LEDs, but only if well heatsinked (high temps degrade the efficiency). BTW, it'll burn up in seconds if not minimally heatsinked. LEDs aren't a miracle of efficiency though, they're in the same neighborhood as efficient incandescents and well below the efficiency of flourescents.