Some experiments with new possibilities of Blender 2.5.alpha 2. It's alpha so it is has many bugs and of course not all new features are integrated. Maybe it would be interesting.
I'v used simple scene with one point light in it.

This is usual render.

This is usual render without ray tracing. It's of course the fastest form of render, so not very useful.

OK. Ambient occlusion. Multiply. Raytrace. Absolutely nothing interesting about it, except noise have appeared.

Ambient occlusion. Multiply. Approximate.
Rather predictable result -- noise has gone. But still nothing interesting.



Ambient occlusion,add,approximate. Much more interesting.
Those awful shadows have gone, lightning is very cute.
For AO with raytrace the result is very close except noise for small
amount of samples appeared.



environment lightning , approximate, color:white,



and this is stable Blender 2.49b. Rather gloomily Don't you think?
If you switch off color management in Blender2.5 alpha you'll have the same result.



This is also Blender 2.49b
Ambient Occlusion, samples:5, Raytrace, Add, Sky Color