I think a good example to illustrate Ferenterer's point is vitamin E and how it works in the body-

Toconutrienols are a nutrient and precursor form to vitamin E. They can be converted to tocopherols and then used for the classic roles of vit E, but they have more functions than that- toconutrienols are used in the formation of cellular membranes, and in and of themselves, help maintain cellular health and lifespan than say, in the supplementation of vitamin E alone.
See 'What's wrong with vitamin E?' for more elaboration.

The point I'd like to make, to support Ferventerer is, that each nutrient, indeed, like D3 and sunlight, benefits the body in many ways, because of the different functions that they have during the body's conversion and manufacture processes.

Sunlight, of example (or from a good UVB light), induces a regeneration and manufacture process in the skin, and in the midst of that, triggers the skin to release, nitrous oxide, which in the bloodstream helps relax and dilate blood vessels (I believe that is part of the seretogenic effect of stepping outside on a sunny day!). I have not yet heard of oral vitamin d triggering that nitrous oxide release, though it is true that there are observations about it improving heart health.
Cholecalciferol (D3) is a finalized form of the vitamin, and that means that several beneficial effects of getting the skin to manufacture it, are potentially lost.

I think, in a way, we also benefit therapeutically and spiritually when we set time aside to do things in a different way than straight supplementation. The Vit D council, before their website overhaul, put emphasis on using solar lamps (in proper moderation) preferentially to vitamin D3 pill supplementation.

After discussion with other forum-goers who have experience with d3 supplementation and then buying a phillips UVB lamp, I have the desire to do the same for myself.

I think the most obvious danger to ourselves as self-treaters, is buying more into the enthusiasm of the person(s) communicating a subject they are excited about, before we assimilate the depths of their experience and understanding about it. There's also two sides to every coin, yes?

It's where a person goes too heavy in the yin, without yang (or vice versa), that you can end up tipping off of balance.