Attached Link: http://www.renderosity.com/messages.ez?Form.ShowMessage=2326114

I also use them a lot of the time, particulary to add depth to a scene. But then again, it depends on what I'm trying to achieve - and if the effect is too washed out, then I crank'em right back or set them at 0.

The volumetric sphere approach is more controllable, but thick fog this way has a habit of showing the sphere/primitive edge in the fog if you are not careful.

There was an interesting thread here a while back on the different effects you can achieve by just altering the Fall-off and Altitude settings.
See the link at the top.