Autodesk’s new 3dsMax 2011 comes with the newly updated Mental Ray 3.8, but doesn’t expose all of the new features.  In an article for CGSociety, Jamie Cardoso takes a look at it and breaks down what you can and cannot get to from the 3dsMax UI, and some of the details involved.  He gets into such details like:

Although the ctrl_ghost_settings for 3ds Max 2011 come with additional features supported by mental ray such as Final Gather; Image Based Lighting; progressive rendering; Iray; Ambient Occlusion Cache; etc, most of them are still being optimised, fixed and/or not fully integrated. Currently, the features that users may find quite useful for production are the importons and irradiance particles.

via CGSociety – mental ray 3.8 for 3ds Max 2011.