Gary,
Good question, there doesn't seem to be a easy conversion factor, since candlepower depends the beamwidth & illumination and lumens are illumination per area. Someone would need to test individual lights or the manufacturers would have to share the information. Lumens are usually used for LEDs since they are not a focused light, and candlepower for focusable incadensents (halogen, kyrton, zenon). Doing some searching on the net I have found 250-900 candlepower/lumens on a variety of flashlights.
Answering your question about the TwinTasker. The Streamlight operating the Zenon bulb pales in comparison to my Maglite 3-D with a Zenon bulb. The Maglite is very focused and projects a long distance, while the TwinTasker projection is uniform it never chokes down to a tight beam. The Maglite is rated at 28,000 candlepower and 42 lumens. The Twintasker is rated at 70 lumens. Although, I seeing spots right now, looking directly into each flashlight, the Streamlight's bulb looks brighter...I guess I'm done now. /forums/images/graemlins/crazy.gif