Hi there,

Here it is. The new mental ray.
http://www.nvidia.com/object/download-mental-ray.html

After an extensive beta test phase, the final version is available for free (there are some limitations of course, you have to buy it, if you want sequence rendering, pro GPU (Quadro, Tesla) support and network rendering).

First the positives:

• New GPU accelerated GI (brute force) system
• Much simpler interface for the settings (easier to use)
• Improved LIS (Light Importance Sampling) system
• MILA based render passes
• MDL support
• IPR like rendering in viewport (supercool)
• LPE support (Light Path Expressions)
• Some nice additional feature (long awaited)

The negatives:

• Insufficient optimization (performance issues)
  If you don’t have a powerful workstation you won’t be happy.
• MILA shader bugs (really unpleasant),
  I checked it with the latest version, still there. 😦
• Other bugs

I think the new mental ray could be a great rendering engine, a real alternative, just not yet.

A positive thought: here is one of my favorite feature in mental ray:
To create a double sided shader, you only need to connect one MILA shader to another through the Backface Shader input point (one click). 🙂

Cheers, D