Truly productivity enhancing Integrated Development Environment, it's plugin and dropin community make it incredibly versatile. Has integration with most source code control systems and great intelligent code completion/refactoring capabilities. I genuinely realized an increase in productivity using eclipse.
Eclipse spans the spectrum of intensity of development. It can handle proof of concept projects and then turn around and deal with massive software engineering projects with multiple dependencies. Cons: Anything with that kind of scope can overwhelm initial users/beginning programmers.