I saw a cateye el500, which seems to use the same voltage and LED element as the performance or nashbar LED's, this morning during my century. The guy had TWO of them on his bike and the spot it created was about as bright as my specialized 5 watt halogen (with a maglight bulb, not the MR11's) run off of 4 AA's.
Though it did have a pretty cool effect cause the two lights made him look like some kind of automobile. Plus the battery life is arguablely longer.