From what I can tell, the ideal position is not to look directly at it, but have it shining down on your face. Like in the photo of the woman in front of the light here:

http://www.carex.com/item/CCFDL93011.../#.V-GJVzWD0sU

Having it off to the side a little does seem okay, since you're still generally facing toward it.

Interestingly, some of the photos on various manufacturers' websites do not show this sort of exposure, they show people sitting next to a (small) light that is shining on their torsos or on whatever they're sitting next to.

But what you are both saying is making me think. It seems that you need the big light on your face, within 1-2 feet away depending on the light, if you just want to get the full effect in 30 minutes. Sitting farther away (or using a light that is less than 10,000 lux) can still work if you use it for a longer time. So having it on at work for hours would be another approach that gets the same effect, and it doesn't really matter that you have the light on longer if you're going to be sitting there anyway. (It would matter for people whose jobs don't involve staying indoors in one place, like nursing, construction, police/firefighters, or even teaching.)

And I guess it still helps if you use it during daylight hours? In my current office I sit next to a window that faces southwest, so I do get some sun from there, weather permitting. It's just that the sun sets so early. And now that I think of it, I get the most sun in the afternoon, not in the morning.

This is very helpful, I'm getting ideas on how I can make this work. Thanks!