I've just installed PP2012 and am just learning how to use IDL and the other new features (upgraded from P7)  Can anyone point me to some good simple lighting setups that take advantage of IDL, or even threads that illuminate this subject?

You might find this thread helpful:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2839289

I did as suggested, and downloaded BB's free Envirosphere.  Applied a texture (a photo I took), and used one infinite white light at 55%.  The results were very good. 

The disadvantage with IDL is the lack of specular lighting if used on its own.  In such case, a specular light will be necessary to bring out those features.

Or specular reflexion, now with ppro2012 blur reflexion is really fast ;)

I think randym is referring to this post

BEFORE Poser8 we had AO and we had Image based Light.
Both are fake and try to give the illusion of natural light.
They do not, and stay at being, or giving an illusion. Nothing more nothing less.

All light sets, build and sold before Poser8 are useless with IDL,(In Direct Light) that was included in Poser8 and the newer versions.

Using an older light set, and turning IDL to ON in the render settings, is like trying to unscramble scrambled eggs. 

In Direct Light is closest to the light we see every day.
Everything around us diffuses light. (Otherwise the objects would be pure black as in a black hole in space.)

Everything diffuses and reflects light in some way for us to see it.
But Poser?
Poser is pure math.
You throw in a light, and we SEE because of the diffuse color-map-value in the node.
Most objects diffuse at 0.8, so we mostly use 0.8 as the diffuse value.

Most objects are rough, or shine.
We use Bump and displacement to rough objects, and can use specular, or blinn to make them shine.

Ha-ha-, but most shiny objects also reflect.
So we use a reflection node to make them reflect what is around them.

And some object even emit light?
Well we can give them a color in ambient_color, and control the emitting with ambient_value.

The mat room in a nutshell and understandable words.
All other nodes are refinements of the above.

For those that do not have it yet.
Goto BB's free stuff and download his free sphere.
The sphere is a 750 ft wide Poser environment.
And this gives the ILLUSION of how light behaves in air.
Air is full of dust to diffuse light.
Poser has no dust, (pure math remember) so we have to create a dust simulation for Poser lights; the sphere.

Now load the sphere, and load ONE DEFAULT infinite true white light, and you have ONE sun, shining in Posers interface.

This, together with IDL gives the closest one can get to natural light.
Yes, put a sky image on the sphere, but BB explains that on his site.

For all else in your scene, you can get away with diffuse, and bump, and displacement, and specular, and blinn, and reflection as needed.
In an ideal situation, EVERY material should have some ambient.
But mostly we can get away without it as you will see for yourself. . . .

One single default infinite light inside BB's sphere is mostly way overdone in light already and the light has to be reduced to . . . start with something around 50-60% in intensity.

Happy posering