On the left is a single infinite light with a white IBL light.

On the right is a single infinite light and IDL enabled.

The IBL renders faster, has no artefacts and is excellent for "empty" scenes.

The IDL is more accurate, but the color bleed can be overwhelming. In the example, the super-blue sky really drains the other colors.

So, both have their uses to me.

The only thing I don't use anymore at all in PP 2012 is Ambient Occlusion.