I think the headlight washers are supposed to work when you've engaged the windshield washing mechanism. They're really sort of useless, if you ask me, although I suppose that anything that might just wipe grime from in front of a generally rather dim set of headlights (I haven't done the Euro headlight option on mine), can't be all bad.
A few months ago, I was first in line at a stoplight and some loon in the crosswalk chose that opportunity to make loud noises and grab his throat, doubling over as if he were retching, all the while pointing at the front of my car, specifically at the headlight wipers, commenting as loudly as possible about the excess of such an item. Naturally, I chose that moment to run my windshield washers and "wink" at him with my headlights. Pissed him off, I suppose.:p
2003 Dodge Durango SLT
2002 BMW E39 530i Sport
1988 Mercedes 300TE
2003 Chevrolet Suburban