FYI, Consumer Reports had an article all about HID headlights in their April annual auto issue titled "Blinded by the light." The gist of the problem: it's not that HID headlights are brighter. It's that they have a sharp cut-off edge in their brightness pattern. Says the article:

HID headlights tend to define the top of their beams with a sharp horizontal line, compared with most halogens' smoother fade to darkness. Bumpy roads can cause that sharp beam to flash at oncoming drivers and in the mirrors of cars ahead as it bounces in and out of view.

So, do HID lights give more light? Says the article:

Unfortunately, while many HID lights we tested were among the better performers, even the best didn't outdistance the best halogens.

Turns out, the best headlights they measured were the halogen lights on the Mazda Protege5, which lit up a marker at 600 feet. Contrast that with a HID-equipped Audi TT that only illuminated something 200 feet out.