I have a love-hate relationship with local lighting in SL.
Lighting in SL is weird, to an extent probably intentionally. Go in an enclosed room with no windows. Set the sun to noon. Surprise! Your camera is no longer obscura! I'm sure that's intentional, so that you don't have to put lighting everywhere.
Local lighting is treated differently somehow. My choices in SL mean that I do a lot of color matching... and local lighting makes that a pain. Colors that look identical in the SL noonday sun can look totally different at midnight with local lighting. It's enough to make one want to detach one's prim hair...
...but that different treatment can look so good! Take a look at the picture that appears at the top of my blog. Nice... but flat. Now, look at this:
That was taken at midnight in the Rainforest sim, lit by torchlight. It's incredibly flattering to the avatar, and definitely not flat... I mean, it shows depth... um, you know what I mean.
In RL, we see the harsh shadows that result from direct sunlight... and like extraneous background objects, we learn to ignore them--but can't ignore them in photographs, so photographers must take them into account. Similarly, we don't ignore them on the screen—which is no doubt another reason SL doesn't accurately depict sunlight. (Accuracy was one reason people kvetched about the initial versions of the SL client with Windlight; we adapt to the differences in lighting at dawn and sunset, too, but Windlight rubbed our noses in it.)
So, photographers, local lighting is your (fickle) friend... just like RL, come to think of it. (The fashion-minded have noticed this, too; I have heard of local lighting attachments that people wear.)