Greg Zaal published a video tutorial demonstrating how to use HDRI Image Based Lighting in Blender 2.5 utilizing the environment light options.

As a refresh - since Blender 2.5 has a drastically faster raytracer, this concept of a rudimental indirect illumination can be rendered much faster than in the previous 2.4 version. However this still requires the Raytrace approach with Ambient Occlusion and thus is most applicable to simple 3D scenes if render time is concerned.

Greg writes: