Why should I use an IDE?

It really depends on what language you're using, but in C# and Java I find IDEs beneficial for:

• Quickly navigating to a type without needing to worry about namespace, project etc
• Navigating to members by treating them as hyperlinks
• Autocompletion when you can't remember the names of all members by heart
• Automatic code generation
• Refactoring (massive one)
• Organise imports (automatically adding appropriate imports in Java, using directives in C#)
• Warning-as-you-type (i.e. some errors don't even require a compile cycle)
• Hovering over something to see the docs
• Keeping a view of files, errors/warnings/console/unit tests etc and source code all on the screen at the same time in a useful way
• Ease of running unit tests from the same window
• Integrated debugging
• Integrated source control
• Navigating to where a compile-time error or run-time exception occurred directly from the error details.
• Etc!

All of these save time. They're things I could do manually, but with more pain: I'd rather be coding.

Code completion. It helps a lot with exploring code.

I don't think it's fair to do the classic "text editor and console window vs IDE" when "text editor" is really emacs. Most features that are typical for IDE:s are also in emacs. Or perhaps they even originated there, and modern IDE:s are mainly interface improvements/simplifications.

This means that for the original question, the answer is not so clear-cut. It depends on how people at the site in question use emacs, if they mainly use it as a text editor, or if they go all out and use custom scripting, learn the commands for the relevant modes, know about code tagging and so on.

The short answer as to why I use an IDE is laziness.

I'm a lazy soul who doesn't like to do things a difficult way when there is an easy way to do it instead. IDE's make life easy and so appeal to us lazy folk.

As I type code, the IDE automatically checks the validity of the code, I can highlight a method and hit F1 to get help, right click and select "go to to definition" to jump straight to where it is defined. I hit one button and the application, with debugger automatically attached is launched for me. And so the list goes on. All the things that a developer does on a day to day basis is gathered under one roof.

There is no need to use an IDE. It is just much harder work not to.