The code outline is a particularly useful feature of Wolfram
Workbench. It provides a summary of code in a source file, as
shown below. This is a very convenient way to find a particular
function definition in a source file--especially if you
have many functions in your code.

An example of the code outline
The error-reporting features are also very convenient. These show
errors in the source files.

Error-reporting in Workbench
You can place the mouse over any of the markers and get a summary
of the reason for the error. In addition, the error shows up in a
problems-summary window, and Workbench also marks the file
in the project as having errors. These make it easy to track, find,
and resolve errors.
Another useful feature involves text hover with usage
information. If you place your mouse over a symbol, the usage message
for that symbol will be displayed. This is a very convenient way to
get function usage assistance.

Text hover with usage information