I figured I'd comment here since I have disabled my DRL's (at first using the ghetto e-brake method, now it's actually rewired properly). I find that DRL's can be useful in certain applications. Take my Acura RDX for example. It has DRL's, but they are a separate bulb independent of the headlights. (In the Acura's case, the DRL's are the high beam bulbs operating on low wattage [the projector HID headlights are low beam only]). This way it's obvious when you use your high beam flash that you are trying to get the attention of the other drivers headed in your direction. For this reason, I disabled the DRL's in my 4Runner (as well as the addition of HID's/ somewhat for looks, but that's another can'o'worms), simply because a low beam (basically DRL) to high beam flash will not be as noticeable as a no beam to high beam flash. If the 3rd gen headlight was multi-chambered and designed to accommodate a bulb for DRL and a bulb for low/high beams, I'd keep the DRL's enabled. Manufacturers are on the right track with DRL's, but some could've been designed more effectively than the 4Runner's. Although I can't tell you how many times I see people driving newer Subaru's, Honda's and Pontiac's at night with NO lights on (ahem...except their DRL's...apologies). Main beam DRL's with those cool always backlight Optitron gauges that are getting more popular in car still seem to confuse a LOT of the population...
And techno, having headlights on during the day isn't necessarily the best way to go either. This may just be one of my pet peeves, but it really pisses me off when people drive during the day with their lights on. While it may improve the ability of people to see you coming, it sure doesn't help the people behind you. It's harder to tell if you're hitting the breaks or not, and have been in the car with two separate people who rear ended the car in front, in the early or mid afternoon, simply because they couldn't tell if the car in front was breaking. Both cars involved had their lights on (and were operational) but again, it comes down to the drastic difference between a bulb being lit and a second filament brightening it a bit and a bulb switching from OFF to ON. Volvos and Saabs are guilty of this.