Please also remember WHY the headlamp washers are fitted .... and I don't just mean for legal reasons ... 
HID lights are DIFFERENT .. and they are badly affected by even small amounts of crap on the lenses, far more than normal halogen lights are.
The deterioration in "cast" light is subtle and can easily not be noticed until it is really poor.
I'd hate to think someone had a serious accident simply 'cos they fitted HID's to "look good" and were driving with restricted vision due to simply dirty lenses.
Just my opinion .. thats all

I disagree....HID light is exactly that....light i.e. photons its just generated using a discharge method rather than a incandescent filament.
Its not affected differently at all because photons are photons!
The only thing you might be able to state is that because there is 3 times the light output that any dirt will drop the light by a set percentage so the light drop off will be more noticeable but, you have to loose a lot to get down to the levels of a standard halogen lamp!
The importnat thing is maintaining the correct adjustment for the headlight but, this is trus of those with auto leveling anyway 
Sorry Mark, I disagree. HIDs are adversely affected in my experience. Having owned both halogen and HID Omegas, my experience confirms this. Same applies to others where I've driven both types - beemers, LRs, mercs, veccys...
The washing system is there for a reason

Also, your legalities thread implies that any retrofit has to be to same standard as if fitted new....
However, if fitted well, and not set so high/right to be selfishly idiotish, who will ever know? But defo worth fitting washers as well
