This new 7.5 release is for current 3ds Max subscription customers.
From the announcement:
Release 7.5 provides new and enhanced functionality in three key areas:
* Autodesk VIZ - With the very latest technologies from Autodesk VIZ 2006, product designers, architects, inventors and others in the design visualization arena have the advanced modeling, lighting, rendering and animation tools that are exclusive to 3ds Max combined with the unique design-oriented functionality of Autodesk VIZ 2006 - all in a single package.
* mental ray 3.4 - Delivering numerous optimizations, mental ray 3.4 will include faster final gathering performance, double precision computation for ray tracing and fast rasterization for first-generation rays. mental ray 3.4 also adds Satellite Rendering, to allow 3ds Max license oweners to freely use up to eight slave CPUs to render an image using distributed bucket rendering
* Hair and Fur - Based on Joe Alter's highly regarded "Shave and a Haircut" solution, Hair and Fur offers numerous styling and dynamics tools for creating amazingly realistic hair and other strand-derivative effects.
In addition to the added functionality above, subscription members will also receive access to multiple e-learning tools and the previously released Cloth Extension for 3ds Max 7, a sophisticated cloth simulation system that gives artists the creative tools to build realistic, film-quality clothing for characters.