SimMechanics is a multi-body simulation tool, that allows mechanical, Control and system engineers to design and test their product.
I've compiled a short hebrew presentaion and demos that show what is SimMechanics, how and when to use it, and what its advantages are. The entire recording can be found here:
SimMechanics enables creation of simulation, while emphasizing the different parts and the connection between them, instead of solving the mathematical equations. Basically, you connect a few bodys using a degree of freedom, run the simulation, and get the results. In the background, MathWorks developers and SimMechanics solve all the different equations for you, using Modal Analysis, and other unique methods.
SimMechanics also allows to import CAD models from SolidWorks, Inventor or ProEngineer, which is a very fast way to pass models (not data) from the mechanical designer to the controls engineer.