Wolfram Workbench is a very good and powerfull tool. It provides a great integrated development environment for developers. A lot of functions and plugins make it more efficient and productive. Integration with other softwares and tools is very easy and seamless. As wolfram is widely used now a days, hence descent support it available.

The fact that it can do both numerical and theoretical calculations easily, compose test, make applets that you can view and use in iPad too. The connectivity with wolfram alpha is a nice bonus!

It has a very powerful syntax, and is extremely customizable functional programming paradigm. It is a great tool for visualizations