The marketing note I received says:

What is Sun Studio?  Previously known as the SunOS compilers,
SPARCworks, Sun Workshop, Forte Developer, and Sun ONE Studio,
Sun Studio 12 includes the following key components:

  * Parallelizing C, C++, and Fortran compilers
  * Next-generation IDE based on NetBeans 5.5.1
  * Code-level debugger
  * Memory debugger
  * Performance profiler
  * OpenMP support
  * Optimized libraries, including Sun Performance Library
  * Multithreading tools

It also lists the following enhancements:

  * Brand new IDE
  * Compilers for Linux (first ever!)
      [ the first production versions of C, C++ and f95 for Linux from
Sun, anyway ]
  * New multithreading/multicore tools, including the new Thread
Analyzer
  * Outstanding Performance- up to 25% increase over Sun Studio 11
     (& up to 80% over GCC 4.1)
  * Improved GCC compatibility to ease adoption