I think it helps when you are facing the sun. BUT I also think that all vehicles should have HID headlights and LED lamps throughout as standard equipment.
A number of large truckload carriers used to set their units to always have headlights on when running. I have not noticed it over the last few years nearly as much. If the driver has no override this could be annoying if parked and idling?
My 1998 Chevy had the DRLs as part of the headlight system. The DRLs operated at 80% of full headlight illumination and were always on unless the switch for the headlights was on. I installed a toggle switch so I could control it.
My 2004 Chevy has the DRLs as part of the amber running/turn signal assembly and is capable of manually controlling them. One advantage to the headlight DRLs on my 98 was the ability to run them at 80% illumination at night during heavy snow or dense fog in conjunction with my fog lights. Less reflective glare.
my DLR'Scome on when the parking brakes release.As long as the parking brakes are on,lights are out.I also have my DLR"S hooked to the front turn signals,not the head lights,that way i can flash my head lights when someone passes