"Linux infrastructure was heavily used in Avatar's graphics rendering done by Weta Digital [...] The Data Center of Weta Digital was re-built in 2008 and consists of 34 racks and more than 4,000 Hewlett-Packard blade servers with a 104TB of RAM. Ubuntu is at the core of all of this, running on all of the rendering nodes, and 90% of the desktops at Weta Digital, according to Paul Gunn, the data center's systems administrator."

http://jordanopensource.org/freeplanet/article/ubuntu-linux-...

I stand corrected (though the one I've used most myself -- Max -- isn't on Linux). I'm not a 3D artist; I just use 3D models in games, and so have only really looked at free options. Which, when I last looked, were somewhat shabby. I just want someone to make a decent but free 3D model editor that supports skeletal animation (sorry, Sketchup).

The remainder, however, are still unchallenged. Photoshop is considered unchallenged on the PC (though for what I do I like Corel PhotoPaint), so I think it would make quite a splash if it were challenged on Linux.