Ugh, hard topic!!
Here's what I think...we are biologically designed to make it through a winter without supplementation. SO, if we are still deficient (after you correct for environmental/cultural factors like being indoors too much, wearing sunscreen, polution which may limit your natural Vit D absorption, dark skin, etc) then something is biologically WRONG. What I mean is, we have to work harder to get enough natural Vit D because of our lifestyles, but it should still be possible. And our bodies are designed to store it over the winter, even eskimos in northern alaska are not walking around with rickets.
BUT...you can't deny what the research is saying about Vit D and its effects on overall health. So then my stance was "I shouldn't need it, but will it hurt anything?" And my answer is...I don't know.
I doubt that it will hurt, but I have concerns about taking it orally when we are designed to absorb it through our skin. I don't like taking anything artificial (including vitamins) but when I do I at least want it to enter my body the way it was intended to. Does that make sense?? I mean, how does our body metabolize Vit D when taken orally vs when absorbed through the skin?? And Vit D isn't actually a vitamin, it's a hormone, so how is it manufactured into pill (or liquid) form???
These are the questions that are bothering me.
I have decided that I'm comfortable enough (not fully comfortable, but enough) with supplementing myself and my two older boys. But I will not supplement Gavin as long as he still has a Virgin Gut. There are so many benefits to the virgin gut, I won't compromise it for Vit D. Now, if I ever have to give him something else (tylenol, antibiotic, nystatin, iron) then I'll probably start supplementing with Vit D then.
Until then, I was very cognizant of this when pregnant and got lots of Vit D exposure myself so he and I would have adequate stores. I also have been ensuring to get him into direct sunlight as often as possible, even if it's just his face because it's too cold. I know that it's not much, but every little bit helps. Oh, and whoever mentioned the window (doser?) beware that many are tinted or otherwise treated and block the sun rays that we need for Vit D. It will still help with Jaundice, but not Vit D.
This is what I believe today...but Vit D is such a confusing topic (so much contradictory information out there, and it just goes against biology in my opinion) so I'm continually researching and I may change my mind at some point.
Also...Dr Mercola sells Vit D sprays and Vit D lamps on his webpage. The lamps are very expensive though!! But guess what I recently discovered...my local grocery store has one! I've noticed it before, it looks like flourescent bulbs hanging on the wall over a bench. I remember thinking it was odd, why are there lights on the wall in a well-lit room?? Then I realized it's a SADD light. A lot of mental health/counseling buildings have them, too, I remember the counseling dept at my college had one that anyone could some sit under. I used to take my homework and go sit under the light for a while a few times a week (I went to school in the Upper Peninsula of Michigan where we got virtually NO Vit D for up to 7 months out of the year). A friend of mine locally bought a lamp from Mercola's webpage and she "barters" it out, if you come to her house to babysit her kids you can sit under the lamp for as long as you want

It's a good deal for her! LOL! I haven't researched the spray yet, but I want to, because that removes my concern about how it is absorbed.