A couple of general comments / random observations from reading back through the thread...
- As with all things, I'm sure the pattern forming LED headlights provide superior illumination and hopefully, reduced glare when new. Gradual clouding of the outer polycarbonate lenses of headlamps seems to be almost inevitable at some point as the car ages, either from Solar UV or from cumulative impact or road grit, probably both. At that point you will end up with extremely bright light sources with diffusers in front of them. No matter how well the beams are controlled, this is bound to greatly increase the dazzle factor for oncoming drivers. Yes, of course this is a factor in halogen lamps too, but the lower brightness and colour temperature probably makes this less objectionable. We may end up with a situation where sealed headlamp systems start failing vehicle inspections much sooner than we are accustomed to.
- Given that the life of halogen bulbs is typically rated in the low hundreds of hours, the suggested LED lifetime figure of 15k hours is very dubious. The number of halogen bulb changes in the lifetime of a typical car can usually be counted on the fingers of one hand. I'm sure that manufacturers will prioritise brightness (and phosphor light output decline) over lifetime, to bring it more in line with the expected life of the rest of the car. Clocking up 15k hours of accumulated driving time, spread over any number of cars, makes it almost inevitable that driver will die the wheel - assuming a very pessimistic 50:50 day:night ratio, that comes to somewhere between 1 and 2 Million miles!
- For those with a sensitivity to the glare of high colour temperature lights, HID or LED, polarized light yellow tinted driving glasses make things a lot less painful. Yes, there must be some minimal light attenuation, but the reduction in dazzle offsets this, it takes the edge off blue tinted oncoming headlights while favouring the colour temperature of your own halogen headlights.