Maya is 'Renderman compliant.' 3dsMax and the others aren't at this time. Maya users can purchase the Renderman plugin for about a thousand dollars. It's supposed to render pretty fast  compared to Mental Ray. I wonder if it would be quick enough to make quality desktop animation feasible, but that's another topic for another board. 

Download my free stuff here: http://www.renderosity.com/homepage.php?page=2&userid=323368