Easier debugging, faster code navigation, better refactoring tools, auto complete, inline documentation, tighter integration of unit tests, and probably many ot

Easier debugging, faster code navigation, better refactoring tools, auto complete, inline documentation, tighter integration of unit tests, and probably many other features I'm not thinking of. Sure I write one off python/ruby/ps scripts in notepad++, but for me any project of real size and complexity will receive a huge productivity boost from a well configured IDE.