The problem with HIDs is that it gives the illusion of greater visibility. It greatly enhances foregroud visibility but because of that fact your eyes get used to the increased foreground visibility and they arent as tuned to the places where your headlights dont go.
heres a quote from daniel stern
"The second point is even more crucial. You remember from above my statement that the eye has a different job to do at night than during the day; here's where that comes into play.
During the day, pretty much everything is illuminated relatively evenly. If it's sunny out, everything's bright. If it's cloudy out, contrast is reduced and colors are muted. If it's foggy out, everything's fuzzy. But at night, your world consists not of "everything", but of that which is illuminated by your headlamps. Everything outside of that "world" is dark. Which is fine, except that your "world" moves with you! The extreme contrast between your "world" (that which is illuminated) and everything else (not illuminated) creates the difficulty. That's why we have headlamp glare at night, why we squint when we come out of a movie theatre after watching a perfectly bright screen for 3 hours, why we hold our hand in front of our eyes when looking in the direction of the sunset and trying to read a road sign. It happens on that big scale (inside/outside your "world") and it also happens *within* that "world".
If you illuminate the foreground very strongly, your eyes will adapt to that big area of strong illumination, your pupils will become smaller, and your distance vision will be reduced. (On the other hand, if you take the route prescribed for so long by US headlamp regulations and have very LITTLE foreground illumination, you'll have a "black hole" in front of the car, and you'll be straining to see what you're about to run over...) "
http://www.danielsternlighting.com/tech/bulbs/Hid/disadvantages/disadvantages.html
i suggest that all of you read it hes a pretty well renowned headlight expert and its an interesting read to say the least.