Mathematica is the tool of choice across the technical world for everything from simple calculations to large-scale computations, programming, or presenting. Throughout industry, government, and education, two million people - from students to Nobel Laureates - use Mathematica to achieve more.
Mathematica seamlessly integrates a numeric and symbolic computational engine, graphics system, programming language, documentation system, and advanced connectivity to other applications. It is this range of capabilities - many world-leading in their own right - that makes Mathematica uniquely capable as a 'one-stop shop'? for you or your organization's technical work

What's New ?
New menu options and an interactive wizard for deploying to CDF
New functions CDFInformation and CDFDeploy for programmatically deploying CDF files
New download progress indicator for the CDF browser plugin
Improved stability, speed, and security of the CDF browser plugin
Tested under Mac OS X 10.7
Improved memory use of the Share function when storing large sets of data
Updated MKL library to improve performance
New syntax coloring to warn about use of Module variable in Dynamic
Performance improvements to citation functions
Improved behavior of optimized variables in compiled conditional statements
Improved front end behavior when saving untitled notebooks under new versions of Linux

How to use the keygen. (It's up to use if you use Parallels Desktop, VMware Fusion or Crossover or whatever)

1 - When you launch Mathematica click on the Other ways to activate button along the bottom left of the window

2 - Click on Offline activation

3 - Copy the MathID you see at the end of the Mathematica window's step 1 text into the keygen

4 - Paste the MathID into the top box in the keygen and click the Generate button

5 - Copy the Activation text from the left box in the keygen into the Activation field in Mathematica

6 - Copy the Password text from the right box in the keygen into the Password field in Mathematica

And voila, click on the Activate button in Mathematica and you're done like dinner